Xavier Moya, University of Cambridge
Christian Bahl, Technical University of Denmark
Jun Cui, Ames Laboratory, Iowa State University
Emmanuel Defay, Luxembourg Institute of Science and Technology
aixACCT Systems GmbH
ES8.1: Magnetocaloric Materials
Tuesday AM, April 18, 2017
PCC North, 200 Level, Room 226 B
10:30 AM - *ES8.1.01
CaloriCoolTM—The Caloric Materials Consortium
Vitalij Pecharsky 1 Show Abstract
1 Ames Laboratory and Department of Materials Science and Engineering, Iowa State University, Ames, Iowa, United States
Caloric materials encompass reversible thermal effects triggered in solids by magnetic, electric, and/or stress fields. Taken separately or together, caloric effects are in the foundation of transformative solid-state cooling technologies that have the potential to realize substantial energy savings in the United States and worldwide upon adoption and deployment by heating, ventilation, air conditioning, refrigeration, and gas liquefaction industries. In addition, caloric refrigeration offers real environmental benefits. Successful rollout of caloric cooling technologies is, however, inhibited by the unavailability of high-performing caloric solids, lack of effective material-device integration pathways, and unknowns related to scarcity of reliable economic and environmental analyses.
The newly established caloric materials consortium – CaloriCoolTM – is a member of the U.S. DOE Energy Materials Network that aims to dramatically decrease the time-to-market for advanced materials innovations critical to many clean energy technologies. CaloriCoolTM is focused on applied materials genome-based rapid discovery of magnetocaloric, electrocaloric and elastocaloric materials, evaluation of in-device performance and most efficient pathways for material-device integration, processing and scale-up, and initial materials-centric application, economic, and environmental analyses. Here, we will provide a high-level overview of CaloriCoolTM organization and capabilities, goals and objectives set to be accomplished over the next five years.
CaloricCoolTM is supported by the Advanced Manufacturing Office of the Office of Energy Efficiency & Renewable Energy of the U.S. Department of Energy. Ames Laboratory is supported by the Basic Energy Sciences Programs of the Office of Science of the U.S. Department of Energy under contract No. DE-AC02-07CH11358 with Iowa State University.
11:00 AM - *ES8.1.02
Magneto-/Mechano-Caloric Effects in All-d-Metal Heusler Shape Memory Alloys
Enke Liu 1 2 , Zhiyang Wei 1 , Catalina Salazar Mejia 3 , Mahdiyeh Ghorbani-Zavareh 2 , Zhaosheng Wang 3 , Jian Liu 4 , Xuekui Xi 1 , Wenhong Wang 1 , Guangheng Wu 1 , Xixiang Zhang 5 , Claudia Felser 2 , Stuart Parkin 6 Show Abstract
1 Insititute of Physics, Chinese Academy of Sciences, Beijing China, 2 , Max-Planck Institute for Chemical Physics of Solids, Dresden Germany, 3 Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden Germany, 4 Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo China, 5 , King Abdullah University of Science and Technology, Thuwal Saudi Arabia, 6 , Max Planck Institute of Microstructure Physics, Halle Germany
Caloric effects, driven by different external fields in phase transitions, are drawing increasing attentions from solid-state cooling in recent years. Developing new phase-transition materials with large caloric effects is one of the important research activities. Recently,1,2 by introducing d-metal element Ti into binary NiMn martensitic alloys, we developed a new family of magnetic shape memory alloys of all-d-metal Heusler Ni(Co)-Mn-Ti. The magnetostructural martensitic transformations can be tuned around room temperature with rich field-induced physical properties. In this talk, I will show the caloric effects of this kind of materials under different external fields of hydrostatic pressure, axial stress, and pulsed magnetic field. A pressure driving efficiency of dTt/dp ~ 56 K/GPa was obtained based on the large volume change of Δω ~ 2% during the hydrostatic pressure. Consistent large adiabatic temperatures of 10 K and 9 K were, respectively, observed during the axial loading and the pulsed magnetic field. Large multi-caloric effects can be gained in these all-d-metal Heusler Ni(Co)-Mn-Ti alloys based on the strong magnetostructural coupling. Furthermore, thanks to the isotropic d-d covalent bonding, the all-d-metal materials show excellent mechanical toughness, which endows the materials high machinability and fatigue resistance, and will further benefit the practical cooling applications as working substance or parts.
1. Z. Y. Wei, E. K. Liu*, et al, Appl. Phys. Lett. 107, 022406 (2015)
2. Z. Y. Wei, E. K. Liu*, et al, Appl. Phys. Lett. 109, 071904 (2016).
11:30 AM - *ES8.1.03
Characterization of Magnetocaloric Materials
Bruck Ekkes 1 , Niels van Dijk 1 Show Abstract
1 , TUD, Delft Netherlands
Large adiabatic temperature changes and large isothermal entropy changes in low magnetic fields are of great interest for heat pumps and energy conversion.
Magnetocaloric materials are being studied with magnetic measurements for decades. With the advent of giant magnetocaloric effects (MCE) that occur in conjunction with magneto-elastic or magneto-structural phase transition of first order, characterization of these materials has become more challenging. The standard magnetization measurements at discreet temperatures may lead to significant overestimation of the MCE.
A well-defined measurement protocol can help to avoid these pitfalls, or one measures the temperature dependence of the magnetization in various applied magnetic fields. As we deal with possible changes in crystal structure, additionally, one needs to characterize the crystallographic structure above and below the Curie temperature by x-ray or neutron diffraction.
As both the entropy change and the temperature change are important parameters for the performance of heat pumps, thermal characterization should also be considered. Specific heat measurements in applied magnetic field are rather difficult but can serve as an independent method to confirm the entropy change determined from magnetic measurements. Additionally, one can derive the adiabatic temperature change from these measurements.
The coefficient of refrigerant performance as figure of merit for magnetocaloric materials shall also be discussed.
1. L. Caron, et al., On the determination of the magnetic entropy change in materials with first-order transitions. JMMM, 2009. 321(21): p. 3559-3566.
E. Brück et al, A universal metric for ferroic energy materials, Phil.Trans. R. Soc. A, 2016 374: 20150303
ES8.2: Electrocaloric Materials
Tuesday PM, April 18, 2017
PCC North, 200 Level, Room 226 B
1:30 PM - *ES8.2.01
Lead Scandium Tantalate as an Electrocaloric Testbed Material
Sam Crossley 1 , Bhasi Nair 1 , Roger Whatmore 2 , Xavier Moya 1 , Neil Mathur 1 Show Abstract
1 , University of Cambridge, Cambridge United Kingdom, 2 Department of Materials, Imperial College, London United Kingdom
We link temperature, field and entropy on high-resolution maps near the room-temperature ferroelectric phase transition of lead scandium tantalate, a well known electrocaloric material. By driving the transition in accessible regions of phase space, and accounting for small irreversibilities, we find large coefficients of performance for regenerative cooling cycles.
2:00 PM - *ES8.2.02
Nanostructured Ferroelectric Polymer Nanocomposites Exhibiting Giant Electrocaloric Effect
Qing Wang 1 Show Abstract
1 , Pennsylvania State University, University Park, Pennsylvania, United States
The electrocaloric effect (ECE), i.e., the reversible thermal changes of a polarizable material upon the application and removal of an electric field, can be exploited to develop solid state on-chip cooling devices for advanced electronics as well as energy-efficient and environment-friendly refrigeration as an alternative to conventional vapor-compression technology. We will present our most recent work on the synthesis of nanostructured ferroelectric ceramics exhibiting colossal ECE at room temperature. Additionally, ferroelectric ceramic nanofillers, such as BST, have been introduced into the ferroelectric polymers as a new class of EC materials. The ceramic-polymer nanocomposites exhibit remarkable room-temperature EC properties, including a cooling energy density of 129.2 MJ m-3 and an adiabatic temperature change of temperature change of 50.5 oC, as a result of greatly improved breakdown strength in comparison to ceramic thin films. Simultaneously, the EC strengths of the nanocomposites are enhanced by the ceramic nanofillers, which enables the generation of sizable ECE under relatively low electric fields. By using ferroelectric relaxor PMN-PT as the nanofillers, the nanocomposites exhibit significantly enhanced ECE in a wide temperature range from 0 to 60 oC with excellent cooling efficiencies. Substantial enhancements in electric displacement and cooling energy density due to the interfacial coupling effect have been demonstrated in the nanocomposites. The effect of the structure and morphology of ferroelectric ceramic nanifillers on ECE of the nanocomposites will be presented.
2:30 PM - *ES8.2.03
Recent Progress on Electrocaloric Multilayer Ceramic Capacitor Development
Sakyo Hirose 1 , Tomoyasu Usui 1 , Sam Crossley 2 , Bhasi Nair 2 , Xavier Moya 2 , Neil Mathur 2 Show Abstract
1 , Murata Manufacturing Co., Ltd., Yasu, Shiga Japan, 2 , University of Cambridge, Cambridge United Kingdom
Ever since the discovery of large electrocaloric (EC) effects in thin films of Pb(Zr,Ti)O3  and ferroelectric copolymers , where changes of electric field produce adiabatic temperature changes of |ΔT | = 12 K, EC materials have been attracting significant attention due to their potential exploitation in the next generation of solid-state cooling devices with high energy efficiency. EC multilayer capacitors (MLCs) can be used to pump a large amount of heat because the many ferroelectric layers are thin, the inner electrodes provide thermally conducting pathways, and the inactive thermal mass is small [3-4]. However, there has been little experimental research on the EC properties of MLCs based on good EC materials. We have fabricated MLCs based on various ferroelectric materials, such as 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMN-PT) and (Pb,Ba)ZrO3 (PBZ), achieved good adiabaticity via geometrical optimization based on finite element analysis of heat flow, achieved high breakdown strengths of over 20 V μm-1, and measured EC temperature change directly using thermocouples and infrared cameras. In 19-layer MLCs, we find |ΔT | = 2.7 K for 0.9PMN-0.1PT at 380 K, and |ΔT | = 3.8 K in PBZ at 430 K. These types of MLC are suitable for testing in prototype cooling systems.
 A. Mischenko et al. Science 311, 1270 (2006).
 B. Neese et al. Science 321, 821 (2008).
 S. Kar-Narayan et al. Appl. Phys. Lett. 95, 242903 (2009)
 R. I. Epstein et al. J. Appl. Phys. 106, 064509 (2009)
3:30 PM - *ES8.2.04
Relaxor-Ferroelectric Ceramics for Efficient Electrocaloric Cooling
Barbara Malic 1 2 , Marko Vrabelj 1 , Lovro Fulanovic 1 2 , Hana Ursic 1 , Silvo Drnovsek 1 , Mojca Otonicar 1 , Jurij Koruza 3 , Vid Bobnar 1 2 , Brigita Rozic 1 , Zdravko Kutnjak 1 2 Show Abstract
1 , Jozef Stefan Institute, Ljublijana Slovenia, 2 , Jozef Stefan International Postgraduate School, Ljubljana Slovenia, 3 Institute of Materials Science, Technische Universität Darmstadt, Darmstadt Germany
Since the discovery of the giant electrocaloric (EC) effect in PbZr0.95Ti0.05O3 thin films , the interest in the effect and in its application, mainly in the cooling technology, has tremendously increased. For cooling applications, however, bulk ceramic samples are a viable alternative due to their larger volume/mass and absence of any substrate, as recently evidenced by a demonstrator device . The ceramic microstructure plays a crucial role in tuning the functional properties of numerous electronic materials; examples include the dielectric grain size effect chemical homogeneity and/or presence of impurities which are ubiquitous in conventional powder-based ceramics processing influencing the dielectric properties of various perovskite ferroelectric materials.
Microstructural descriptors, i.e., grain size and grain size distribution, impurities, porosity, domains, and the chemical homogeneity influence the EC effect of lead-based relaxor ferroelectric 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMN-10PT) ceramics with grain sizes in the micron range. The EC temperature change of 3.45 °C at 160 kVcm-1 and 127 °C is the highest reported value for the Pb-based perovskites, and it was obtained for the material with the relative density of about 98 % and 3.6 µm sized grains, prepared by atmosphere-sintering the mechanochemically activated powder compact . The PMN-10PT material in the form of multilayer (ML) elements and with a dense and uniform microstructure, exhibits a comparable EC response to the bulk, yet at a much lower applied voltage as a consequence of reduced element thickness enabled by the tape-casting technology .
In the contribution we address combined effects of chemical composition, processing and details of the microstructure on the resulting dielectric and electrocaloric response of selected lead-based and lead-free perovskite relaxor-ferroelectrics.
 A. S. Mischenko et al., Science, 311, 5765, 1270 (2006).
 U. Plaznik et al., Appl. Phys. Lett., 106, 043903 (2015).
 M. Vrabelj et al., J. Eur. Ceram. Soc., 36, 1, 75 (2016).
 L. Fulanović et al., J. Eur. Ceram. Soc., 36, 1, 75 (2016).
4:00 PM - ES8.2.05
Electrocaloric Effect in Lead-Free Ferroelectric Ceramics Measured Directly
Mehmet Sanlialp 1 , Vladimir V. Shvartsman 1 , Doru Lupascu 1 Show Abstract
1 , University Duisburg-Essen, Essen Germany
Large heat dissipation in miniaturized microelectronic devices reduces the performance of the applications. Hence, demand for energy-efficient refrigeration technologies with a reduced environmental impact have stimulated interest to solid-state refrigerators based on the electrocaloric effect (ECE). ECE is the adiabatic temperature change or isothermal entropy change of a dielectric material in a varying external electric field.
ECE based refrigerators should combine high efficiency, low cost, be environmentally friendly and easily scalable for future applications. Therefore, considerable effort is made to develop new cooling devices in order to reach better efficiency than the conventional cooling technologies.
In this presentation, we report on development of two direct ECE measurement methods. Firstly, a custom built quasi-adiabatic calorimeter to measure directly the temperature change of the sample. Secondly, a modified differential scanning calorimeter1, which is able to measure the entropy change in isothermal condition. The setups allow measurements in the temperature range 230-420 K at applied electric fields up to 40 kV/cm.
We performed the ECE measurements in several lead-free ferroelectric systems:
BaTiO3 with Sn-doping,
BaTiO3 with Zr-doping.1
Temperature, electric field, and composition dependences of the ECE have been studied. Furthermore, we compare results of the direct ECE measurements with frequently used indirect predictions based on Maxwell relations to judge the compatibility of these measurement methods.
1. Modified Differential Scanning Calorimeter for Direct Electrocaloric Measurements, M. Sanlialp, C.Molin, V.V. Shvartsman, S. Gebhardt, D. C. Lupascu, IEEE TUFFC, 2016.
2. Strong electrocaloric effect in lead-free 0.65Ba(Zr0.2Ti0.8)O3-0.35(Ba0.7Ca0.3)TiO3
ceramics obtained by direct measurements, M. Sanlialp, V.V. Shvartsman, M. Acosta, B. Dkhil, D. C. Lupascu, APL, 2015.
4:15 PM - ES8.2.06
Electrocaloric Effect in PZ-Based Antiferoelectrics
Bouchra Asbani 2 , Brigita Rozic 1 , Mimoun El Marssi 2 , Jurij Koruza 1 , Barbara Malic 1 , Rasa Pirc 1 , Zdravko Kutnjak 1 Show Abstract
2 LPMC, University of Picardie Jules Verne, Amiens France, 1 , Jozef Stefan Institute, Ljubljana Slovenia
The electrocaloric (EC) effect has attracted great interest for developing new cooling devices that have the potential to reach better efficiency than the existing cooling technologies [1,2]. In this contribution our direct measurements of the large EC effect in antiferroelectric PbZrO3 (PZ) based ceramics [3,4] will be presented. In addition, EC effect in antiferroelectric n/95/5 PLZT ceramics will be investigated by direct experiments including the compositions with coexisting ferroelectric and antiferroelectric order such as 6/40/60 PLZT ceramics. Here a negative EC response, i.e. opposite response with respect to the electric field change was found in coexistence with the positive EC effect.  Z. Kutnjak., B. Rozic, R. Pirc., Wiley Encyclopedia of Electrical and Electronics Engineering, p. 1-19 (2015).  A. S. Mischenko et al., Science 311, 1270 (2006).  R. Pirc, B. Rozic, J. Koruza, B. Malic, Z. Kutnjak, EPL 107, 17002 (2014).  R. Pirc, B. Rozic, J. Koruza, G. Cordoyiannis, B. Malic, Z. Kutnjak, J. Phys.:Condens.Matter 27, 455902 (2015).
4:30 PM - ES8.2.07
Screening and Reliability of Multi-Layer Capacitors for Electrocaloric Cooling
Romain Faye 1 , Daniele Sette 1 , Herv Strozyk 1 , Emmanuel Defay 1 Show Abstract
1 , Luxembourg Institute of Science and Technology, Belvaux Luxembourg
The electrocaloric community has recently been more and more involved in the development of prototypes in order to demonstrate that electrocaloric effect (ECE) can be used for new kinds of cooling devices. The existing prototypes are based on polymers, ceramics or even commercial multilayer capacitors (MLCs). In this study, we have considered MLCs playing the role of cooling device. The aim has been to identify some key parameters enabling to choose the most appropriate MLCs with respect to prototype design and cycling parameters. To do so, we have been interested in heat exchange, cooling power, efficiency and fatigue behaviour.
Direct and indirect characterizations of ECE have already shown that some MLCs can exhibit a temperature difference up to 1K. Its multilayer design allows for applying large electric fields while maintaining a good “active material/electrode” volume ratio. The commercial availability of this electronic component is also a guarantee of reliability and robustness for standard usage.
We made a screening of different commercial MLCs in order to compare their temperature change, caloric heat and electrical work. We have highlighted that at 200 V temperature change can vary by 30 % between MLCs with the same specification from different providers. By using high frequency Infrared imaging (up to 600 Hz), we also observed the way the caloric heat is emitted or absorbed during the very first second. The maximum temperature change on the surface is reached less than 30 ms after the voltage application. Operating an EC cooling device requires continuous electrical cycling at a voltage value much higher than its standard specification. Depending on the cycling frequency the number of cycle can easily reach few hundreds of thousand per day. So it appears necessary to characterize the unipolar fatigue behaviour of this component and the possible strategy to restore its initial properties. After 500 000 cycles, a 23% decrease in maximum unipolar polarization is observed. Finally, we will provide some elements concerning the strain induced by the application of an electric field. This piece of information can be interesting to define the best way to assemble MLCs together.
These results can be considered as guideline to integrate MLCs into future prototypes.
Xavier Moya, University of Cambridge
Christian Bahl, Technical University of Denmark
Jun Cui, Ames Laboratory, Iowa State University
Emmanuel Defay, Luxembourg Institute of Science and Technology
aixACCT Systems GmbH
ES8.3: Magnetocalorics, Modeling and Materials
Wednesday AM, April 19, 2017
PCC North, 200 Level, Room 226 B
8:30 AM - *ES8.3.01
Caloric Effects from Fluctuating Local Magnetic Moments and Itinerant Electrons Described by Ab Initio Theory
Julie Staunton 1 , Jan Zemen 2 3 , Eduardo Mendive-Tapia 1 , Zsolt Gercsi 2 4 , Karl Sandeman 5 Show Abstract
1 , University of Warwick, Coventry United Kingdom, 2 , Imperial College, London United Kingdom, 3 , University of Nottingham, Nottingham United Kingdom, 4 , Trinity College Dublin, Dublin Ireland, 5 , Brooklyn College and The Graduate Center of CUNY, New York, New York, United States
We discuss the Disordered, Local Moment (DLM) theory of magnetic materials and its quantitative description of the temperature and field dependence of magnetic phase transitions and magnetocaloric effect [1,2]. The intricate interplay between itinerant electronic structure and magnetic ordering of local moments in the theory also enables the variation of the magnetic transitions on both composition and, crucially for other caloric effects, atomic spacing  to be described. To illustrate we model how the application of strain affects the first order ferromagnetic-antiferromagnetic transition in Fe-Rh and estimate the magnitude of the associated strain-induced isothermal entropy change. Lastly we present our conclusions for novel elastocaloric effect-driven cooling cycles potentially available from Mn antiperovskite nitride refrigerants . These are based on the large adiabatic temperature and isothermal entropy changes which we predict for Mn3GaN that arise from the geometrically frustrated interactions between the Mn local moments. As a consequence our calculated temperature-strain phase diagram predicts two new phases, shows both first and second order phase transitions and two tricritical points among paramagnetic, ferrimagnetic, collinear and non-collinear antiferromagnetic states.
 B.L.Gyorffy et al., J.Phys. F 15, 1337, (1985).
 J.B. Staunton et al., Phys. Rev. B 89,054427, (2014).
 J.B. Staunton et al., Phys. Rev. B 87, 060404(R), (2013).
 J. Zemen et al., submitted for publication; arXiv:1609.03515.
9:00 AM - ES8.3.02
Assessing Performance of Caloric Material Refrigerants through Hysteretic Thermodynamic Modeling
Timothy Brown 1 , Patrick Shamberger 1 Show Abstract
1 Materials Science and Engineering, Texas A&M University, College Station, Texas, United States
Caloric materials exhibiting first-order phase transitions can provide a material basis for energy efficient refrigeration cycles. However, evaluation of caloric material performance is challenging, since (1) refrigerant performance necessarily depends on the complete temperature-field cycle used, including the constraints under which external fields vary (e.g., isothermal vs. adiabatic magnetization legs), and (2) substantial thermal hysteresis (1-20 K) in the first-order phase transition not only dissipates input energy and reduces efficiency, but also introduces path-dependent memory effects, which complicate calculation of cycle-dependent properties. Until recently, there has been no clear path to evaluate critical cyclic performance characteristics of different classes of caloric materials and cycles, while fully accounting for the impacts of irreversible aspects of the phase transition on refrigerant performance.
Here, we summarize results calculated for candidate giant magnetocaloric effect (GMCE) materials undergoing magnetic refrigeration cycles from 0 to 1.5 T and 0 to 5 T, using a recently developed modeling framework to simulate key cyclic refrigerant-based figures of merit (potential cooling power, work input, temperature span, % Carnot efficiency). By combining a Preisach rate-independent hysteresis model with a non-equilibrium thermodynamic analysis of phase transformations, we quantitatively investigate the interacting effects of path-dependent state behavior, cycle choice, and physically-meaningful descriptors of GMCE materials’ magnetic and thermal properties, on the refrigeration metrics.
Using this methodology, we: (1) Explore the role of hysteresis behavior, by analyzing materials performance metrics as a function of a simplified two parameter hysteresis model, (2) Evaluate and compare the relative performance of two candidate magnetic refrigeration cycle classes: Ericsson (alternating iso-thermal, iso-field legs) and magnetic Brayton (alternating isentropic, iso-field legs) under the same magnetic field constraints, and (3) Present direct efficiency and energy-based comparisons of the principle classes of GMCE materials (MnFe-based compounds, NiMn-based Heusler alloys, and La(Fe,Si)13 and its hydrides) on an irreversible basis.
As a result, we quantify the effect of transformation hysteresis and elastic width on cycle efficiency for representative alloys from different materials classes, demonstrate the significant impact of this transformation behavior on overall cyclic performance, and establish target thermal hysteresis widths to attain desired cyclic efficiency. Furthermore, cyclic figures of merit are related through simplified but physically meaningful descriptors to a given GMCE material's magnetic and thermal properties, demonstrating the method's use as a materials analysis and design tool.
9:15 AM - ES8.3.03
Localized Modeling of First Order Magnetocaloric Materials with a Distribution in Curie Temperature
Kaspar Nielsen 1 , Christian Bahl 1 , Rasmus Bjork 1 Show Abstract
1 , Technical University of Denmark, Roskilde Denmark
We present a 3-dimensional transient numerical model that spatially resolves magnetocaloric samples down to the grain size. The model includes the demagnetizing field, chemical inhomogeneity realized as a spatial variation of Curie temperature across the sample, local hysteresis and heat transfer. The La(Fe,Si,Mn)13Hy system is used to exemplify and we apply the Bean-Rodbell model as the local state function. We show that even a modest distribution in Curie temperature (TC) across the sample results in a significant broadening and lowering of the total entropy change of the sample around TC. We discuss how clustering of grains with similar TCs across the sample influences the results.
9:30 AM - ES8.3.04
Rare Earth Based Magnetocaloric Refrigerant Materials for Gas Liquefaction
Brandt Jensen 1 , Samuel Wolf 2 , Tyler Slinger 2 , Iver Anderson 1 , Jamie Holladay 3 , John Barclay 4 , Jun Cui 1 Show Abstract
1 Division of Materials Science and Engineering, Ames Laboratory, US-DOE, Ames, Iowa, United States, 2 Department of Materials Science and Engineering, Iowa State University, Ames, Iowa, United States, 3 , Pacific Northwest National Laboratory, Richland, Washington, United States, 4 , Emerald Energy NW, Redmond, Washington, United States
Thermomagnetic properties and heat capacities of 8 rare-earth binary alloys (R = Y, Gd, Tb, Dy, Ho, Er) have been investigated for their use in a magnetocaloric refrigeration system designed for gas liquefaction. Rotating disk atomization of the rare-earth alloys has been employed to produce 150 – 250 µm spherical powders. Chemical analysis and magnetic properties of these powders are used to ensure the powders retain their excellent magnetocaloric properties. The Curie temperatures for all 8 alloys span from 293 K (Gd) to 153 K (Gd0.16Ho0.84) while retaining high saturation magnetization. Heat capacity measurements of the ferromagnetic transitions in fields of up to 6.8T are also employed to help facilitate the thermodynamic modelling of the gas liquefaction system.
10:15 AM - ES8.3.05
Affordable, High Performance Magnetocaloric Nanomaterials and Systems
Raju Ramanujan 1 , Varun Chaudhary 1 Show Abstract
1 , Nanyang Technological University, Singapore Singapore
Magnetocaloric systems represent a class of novel, energy efficient, “green”, thermal management technologies. However, commercialization is limited by the cost of “standard”, expensive, rare earth based magnetocaloric materials (MCM). Hence, we developed iron based magnetocaloric nanoparticles (Fe-Ni-X where X = Mn, Cr and B) with RCP values higher than of giant magnetocaloric materials. (Fe70Ni30)89B11 nanoparticles were found to exhibit very high RCP up to 640 J-kg-1 for a field change ΔH of 5 T with TC ~ 381 K. Broad operating temperature range along with moderate change in entropy and very high RCP make these nanoparticles potential candidates for magnetic cooling applications in low grade waste heat recovery. The MCE of (Fe70Ni30)100-xMnx nanoparticles were measured. The γ - (Fe70Ni30)95Mn5 (TC ~ 338 K) and γ-(Fe70Ni30)92Mn8 (TC ~ 317 K) nanoparticles possess good relative cooling power (RCP) up to 470 J-kg-1 and 415 J-kg-1, respectively, for a field change of 5 T. Good agreement was found between the critical exponents of the γ-(Fe70Ni30)92Mn8 alloy nanoparticles determined by the modified Arrott plot and those obtained from the Kouvel-Fisher method. To further tune the TC, the magnetic and magnetocaloric properties of transition metal based (Fe70Ni30)100-xCrx (x = 1, 3, 5, 6, and 7) nanoparticles were studied. Only 5 % of Cr alloying with Fe-Ni reduce the TC from ~ 443 K to 258 K, the RCP value is 406 J-kg-1 higher than those of Gd nanoparticles (400 J-kg-1) for ΔH = 5 T. Our results demonstrate the feasibility of developing high RCP, low cost, rare earth free magnetocaloric nanoparticles for near room temperature applications. A prototype of self-pumping magnetic cooling based on the thermomagnetic effect was constructed with magnetic nanoparticles in a suspension used as the ferrofluid. It was found that the system performance depends strongly on heat load, magnetic field, volume fraction of particles and density of ferrofluid. Cooling by ~ 27 °C has been achieved by application of 0.3 T magnetic field. These results matched well with our simulations. This technique has considerable potential for electronic cooling applications since there is no external energy input and no moving mechanical part. Our system is self-regulating; as the heat load increases, the heat is transferred from heat source to heat sink more quickly. Energy harvesting could also be performed using this system.
10:30 AM - *ES8.3.06
Recent Developments in Gd Alloy Microwires for Energy-Efficient Magnetic Refrigeration
Manh-Huong Phan 1 Show Abstract
1 , University of South Florida, Tampa, Florida, United States
Magnetic refrigeration based on the magnetocaloric effect (MCE) is a promising alternative to conventional gas compression based cooling techniques . However, existing MCE-based coolers operate at a relatively low operating frequency (~4 Hz), resulting in the low cooling power. Theoretical studies have predicted that reducing the dimensions of a magnetic refrigerator can increase the cooling power of the device by increasing the operating frequency [2,3]. Shaping magnetic refrigerants in the form of spherical or irregular particles is inefficient, due to their high losses on viscous resistance and demagnetization . Mechanical instability of the refrigerant can result in a significant loss of heat throughout due to misdistribution of flow. The use of a bundle of magnetocaloric wires is more desirable as this configuration enables higher mechanical stability and lower porosity. A magnetic bed made of arrayed Gd wires has been theoretically shown to yield a greater temperature span between its ends, which results in a higher cooling load at a higher efficiency, as compared to that made of Gd particles . The use of the wires with increased surface areas also allows for a higher heat transfer between the magnetic refrigerant and surrounding liquid.
In this talk, we discuss our recent experimental studies on the design, fabrication, and characterization of melt-extracted Gd alloy microwires for energy-efficient magnetic refrigeration in the liquid nitrogen temperature regime [4-7]. We have demonstrated that these microwires possess an enhanced MCE relative to their bulk counterparts [4,5]. The magnetocaloric and mechanical properties of the microwires can be improved by creating a biphase structure composed of small nanocrystals embedded in an amorphous matrix through thermal annealing or controlled solidification [6,7]. Since these microwires can easily be assembled as laminate structures, they have potential applications as a cooling device for micro-electro-mechanical systems (MEMS) and nano-electro-mechanical systems (NEMS).
1. V. K. Pecharsky, K. A. Gschneider, and A. O. Tsokol, Rep. Prog. Phys. 68, 1479 (2005).
2. M. D. Kuzmin, Appl. Phys. Lett. 90, 251916 (2007)
3. D. Vuarnoz, T. Kawanami, Appl. Therm. Eng. 37, 388 (2012)
4. N. S. Bingham, H. Wang, F. Qin, H. X. Peng, J. F. Sun, V. Franco, H. Srikanth, and M. H. Phan, Appl. Phys. Lett. 101, 102407 (2012)
5. F. X. Qin, N. S. Bingham, H. Wang, H. X. Peng, J. F. Sun, V. Franco, S. C. Yu, H. Srikanth, and M. H. Phan, Acta Mater. 61, 1284 (2013)
6. H.X. Shen, D.W. Xing, J.L. Sánchez Llamazares, C.F. Sánchez-Valdés, H. Belliveau, H. Wang, F.X. Qin, Y.F. Liu, J.F. Sun, H. Srikanth, and M.H. Phan, Appl. Phys. Lett. 108, 092403 (2016)
7. H. Belliveau, Y. Y. Yu, Y. Luo, F. X. Qin, H. Wang, H. X. Shen, J. F. Sun, S. C. Yu, H. Srikanth, and M. H. Phan, J. Alloys and Comp. 692, 658 (2017)
ES8.4: Electrocalorics, Modeling and Materials
Wednesday AM, April 19, 2017
PCC North, 200 Level, Room 226 B
11:00 AM - *ES8.4.01
First Principles-Based Investigation of the Electro-Caloric Effect
Claude Ederer 1 Show Abstract
1 , ETH Zurich, Zurich Switzerland
The electro-caloric effect (ECE), i.e., a temperature change observed in certain materials under application or removal of an electric field, provides a very attractive prospect for future solid state cooling devices. Here, we use molecular dynamics simulations based on an effective Hamiltonian derived from first principles, to study the ECE in the prototypical ferroelectric material BaTiO3 (BTO). Our studies allow to gain a better understanding of the underlying mechanisms and to identify routes for optimizing the electro-caloric response towards future device applications.
We analyze the ECE in the vicinity of all three ferroelectric transitions in BTO, and we discuss in particular the origin of an inverse ECE (i.e. decreasing temperature under application of an electric field) that occurs for certain orientations of the applied field. We also discuss effects of irreversibility that results from the first order character of the ferroelectric transitions.
Furthermore, we explore ways to optimize the caloric response through epitaxial strain in thin films of BTO. We show that strain can be used to shift the largest caloric response to both higher and lower temperatures, depending both on the type of strain (compressive or tensile) and on the orientation of the applied field. Furthermore, our results indicate an enhanced caloric response due to strain-induced multi-domain formation.
11:30 AM - ES8.4.02
Measurement Artefacts in Electrocalorics
Bhasi Nair 1 , Sam Crossley 1 , Xavier Moya 1 , Neil Mathur 1 Show Abstract
1 Materials Science, University of Cambridge, Cambridge United Kingdom
Electrocaloric effects are reversible thermal changes driven by applied electric fields. Electrocaloric effects tend to be small in bulk materials due to the onset of dielectric breakdown at relatively low applied fields, whereas they tend to be larger in thin films due to enhanced breakdown. However, these larger effects often translate to small signals that are difficult to detect because the thermal mass of thin films is small. Here we describe experimental difficulties and artefacts encountered in the measurement of electrocaloric effects in both bulk and thin films, by different protocols, namely indirect methods based on the thermodynamic analysis of temperature-dependent polarisation data, and direct methods based on thermometry and calorimetry.
11:45 AM - ES8.4.03
Phase Transition Behavior and Electrocaloric Effect in Bismuth Zinc Titanate and Barium Titanate Solid Solutions
Chae Il Cheon 1 , Dae Su Kim 1 , Jeong Seog Kim 1 Show Abstract
1 , Hoseo University, Chungnam Korea (the Republic of)
Relaxor ferroelectrics are disordered crystals with peculiar structures and properties and have been applied to many electronic devices due to their giant dielectric and electromechanical responses. Recently, they attract great attention due to its high electro-caloric effect (ECE) which is change of entropy and temperature by electric field. Pb(Mg,Nb)O3-PbTiO3 (PMN-PT) is one of the mostly investigated relaxor ferroelectrics. A global environment issue demands lead-free relaxor ferroelectrics. BiFeO3-based solid solutions such as BiFeO3-BaTiO3 (BF-BT) demonstrated outstanding ferroelectric and piezoelectric properties at phase boundary between ferroelectric rhombohedral and pseudo-cubic at ~ 0.3BT. It has also been reported that a crystal structure of the BF-BT solid solution changed from pseudo-cubic and ferroelectric tetragonal at ~ 0.9BT. BF-BT solid solutions with a pseudo-cubic phase (x = 0.3~0.9) have been reported to have overall cubic structure with polar nanoregions (PNR) and are expected to show high ECE. Solid solutions between other Bi-based perovskites such as BiScO3 and Bi(Zn,Ti)O3 and BaTiO3 are also reported to show similar relaxor phase transitions near room temperature and expected to have high ECE. A Bi-based perovskite-barium titanate solid solution with a BT-rich composition could be a good candidate for solid state cooling device using ECE because their transition temperatures are higher than room temperature by a few tens of degrees. In this work, phase transition behavior and ECE were investigated in solid solutions between Bi(Zn,Ti)O3 (BZT) and BaTiO3. Samples were prepared by conventional ceramic process. The crystal structure changed from tetragonal to pseudo-cubic around 0.05BZT-0.95BT when the amount of BZT increased. The temperature dependence of permittivity showed that the phase transition behavior also changed from ferroelectric to relaxor around 0.95BT. Polarization-electric field (P-E) hysteresis curves were measured at temperatures of RT ~ 180oC in BZT-BT ceramics with compositions near 0.95BT and temperature changes due to ECE were calculated indirectly with temperature dependences of polarizations using Maxwell relation.
ES8.5: Caloric Devices
Wednesday PM, April 19, 2017
PCC North, 200 Level, Room 226 B
1:30 PM - ES8.5.01
Electrocaloric Cooling Systems—Theory to Demonstration
David Schwartz 1 , Yunda Wang 1 , Jamie Kalb 1 Show Abstract
1 , PARC, Palo Alto, California, United States
As electrocaloric materials improve, there is an increasing need to augment understanding of how to translate high material performance into high system efficiency. This extends beyond maximizing ΔS and ΔT to consideration of thermodynamic cycles and constraints in heat transfer and the electrical system. Based on insights gained in previous experimental work, we will share our analysis of how to approach system design, framing theoretical performance with practical constraints. We will also present new measurement results from an improved experimental device that overcomes some limitations of our previous heat-switch-based design.
1:45 PM - ES8.5.02
Electrocaloric Refrigeration Using Commercial Multi-Layer Capacitors and Fluid-Assisted Thermal Regeneration
Herv Strozyk 1 2 , Romain Faye 1 , Daniele Sette 1 , Mathieu Gerard 1 , Emmanuel Defay 1 Show Abstract
1 , Luxembourg Institute of Science and Technology, Belvaux Luxembourg, 2 , Chimie ParisTech, Paris France
In a time when the global warming cannot be ignored, conventionnal compression cooling devices are regarded with a critical eye. Indeed, utilized fluorocarbon fluids are known to induce global warming and also to act as ozone layer depleting gases. The caloric community is thus trying to move on new techniques. Our work is based on a refrigeration devices exhibiting the electrocaloric (EC) cooling effect. The active material is based on Zr-doped BaTiO3, which appears in commercially available multi-layer capacitors (MLCs). When voltage is applied to the electrodes of the capacitors, they undergo a temperature increase. When voltage is released, the material then cools down. The applied voltage ranges from 100 to 200 V, which corresponds to temperature variation (positive or negative) ranging from 0.5 to 0.8 °C. This nominal effect is then coupled to a thermal regenerator. The function of this device is to use a thermal active substance to create a thermal gradient. The latter is the evidence of the ability of the device to act as a thermal pump. Our device consists of a fluid column partially into a cell that contains the active EC capacitors, and partially into elastomer hoses. The fluid, which is low viscosity silicone oil, is used both as a heat storing material and as heat exchange medium. It is moved back and forth in contact with the MLCs. The motion is provided by a home-made peristaltic displacer based on the motion of a piston. The thermo-fluidic cycle is timed as follows. The top part of the fluid column is in contact with the EC material when the field is applied. Then the fluid is moved up while the field is maintained. When the fluid has reached its top position, the field is released, which infers that the EC material cools down. Consequently, the bottom part of the fluid column is also cooled down. After several repetition of the previous cycle, a thermal gradient takes place between the top and the bottom of the fluid column. This corresponds to the thermal equilibrium with the thermal losses. When 3 blocks of 50 MLCs are used to generate EC thermal regeneration, the best thermal gradient ΔT that can be obtained is 0.21 K after 700 s of running, under 140 V applied voltage. Refrigeration is obtained here, as temperature of the bottom part of the fluid column is decreased. The influence of different relevant parameters on the cooling performances of the system is also analysed. The direct influence of the voltage on ΔT is clear: the larger the voltage and the larger the temperature gradient. The heat exchange is also identified to be important for enhancing EC performances. In our system, this parameter corresponds to the thickness of fluid channels that permit the contact between cooling fluid and active material. The narrower the channel, the larger the speed of the fluid and thus the larger the heat exchange. This prototype gives the opportunity to identify the key design parameters for the next generation of EC coolers.
2:00 PM - ES8.5.03
Improved Performance from Heat Transfer Gas By-Pass Flow during the Cold-to-Hot Flow Step of an Active Magnetic Regenerative Liquefier
Jamie Holladay 1 , John Barclay 2 , Kerry Meinhardt 1 , Edwin Thomsen 1 , Evgueni Polikarpov 1 , Jun Cui 3 , Iver Anderson 4 Show Abstract
1 , Pacific Northwest National Lab, Richland, Washington, United States, 2 , Emerald Energy Northwest, Redmond, Washington, United States, 3 , Iowa State University, Ames, Iowa, United States, 4 , AMES Laboratory, Ames, Iowa, United States
The Pacific Northwest National Laboratory (PNNL) working with Emerald Energy Northwest (EENW), Iowa State University, and AMES National Laboratory will report on the development of a magnetocaloric gas liquefier prototype. The test design has cylindrical reciprocating dual magnetic regenerators configured into an active magnetic regenerative refrigerator toward a gas liquefier that efficiently produces LH2, LNG, LHe, or other cryogenic liquids. The active magnetic regenerator (AMR) cycle of the design consists of four steps: adiabatic magnetization with no heat transfer gas flow; cold-to-hot heat transfer gas flow through the magnetic refrigerant at constant high field; demagnetization with no heat transfer gas flow; and hot-to-cold flow at constant low field. The dual-regenerator prototype has a unique feature that allows a 5-10% of the cold heat transfer fluid (HTF) from the demagnetized regenerator to by-pass the cold-to-hot flow step through the magnetized regenerator. The HTF which by-passes the cold-to-hot flow step is used to continuously pre-cool the process stream before re-entering the HTF flow circuit near the hot temperature of liquefier. Each AMR regenerator in the prototype under test contains ~215 g of magnetic refrigerant; 5 small thermocouples are used to monitor the axial temperatures in the regenerators during the cycle. Results to date indicate about 25% increase in total cooling power using the by-pass feature when operating between 3.3 T to 0.6 T. We will report on measurements of the system performance at 3.3 T and at higher magnetic fields (e.g., up to 6 T) with a single refrigerant when cooling power and bypass flow are varied.
2:15 PM - ES8.5.04
Optimising the Design of a Magnetocaloric Heat Pump
Christian Bahl 1 , Stefano Dallolio 1 , Dan Eriksen 1 , Kurt Engelbrecht 1 Show Abstract
1 DTU Energy, Technical University of Denmark, Roskilde Denmark
A domestic heat pump, based on the magnetocaloric effect, has been designed. The design has been optimised and dimensioned to the requirement of a modern Northern European single family house, with a heating power of 1500 W and a temperature span of about 20 K.
The permanent magnet assembly for the heat pump has been designed through a novel ‘virtual magnet’ approach . The applied flux reaches a magnitude of 1.6 T in the high-field regions, while being close to zero in the low-field regions.
The regenerator beds will be packed with spherical La(Fe,Mn,Si)13Hz particles. Numerical modelling has shown that for the required temperature no improvement in heating power is expected when using more than 10 individual grades of materials . The spheres are bound by epoxy to prevent the breaking apart of the material, due to internal stresses at the phase transition .
Shaping of the beds is optimised to maximise the magnetic flux through them while fully utilising the available gap in the magnetic circuit. The individual filling of the 10 layers is done according to the field distribution and the advantage of this is demonstrated by numerical AMR modelling .
Construction of the heat pump device is ongoing, and it is expected to be operational in the middle of 2017.
 A.R. Insinga, C.R.H. Bahl, R. Bjørk and A. Smith, Globally Optimal Segmentation of Permanent-Magnet Systems, Phys. Rev. Applied 5, 064014 (2016)
 T. Lei, K.K. Nielsen, K. Engelbrecht, C.R.H. Bahl, H. Neves Bez, C.T. Veje, Sensitivity study of multi-layer active magnetic regenerators using first order magnetocaloric material La(Fe,Mn,Si)13Hy, J. Appl. Phys., 118, 014903 (2015)
 H.N. Bez, K.K. Nielsen, A. Smith, P. Norby K. Ståhl and C.R.H. Bahl, Strain development during the phase transition of La(Fe,Mn,Si)13Hz Appl. Phys. Lett. 109, 051902 (2016)
 S. Dall’Olio et al. (To be published)
3:30 PM - *ES8.5.05
Highly Efficient Caloric Devices
Nini Pryds 1 , Kurt Engelbrecht 1 , Dan Eriksen 1 , Rasmus Bjork 1 , Kaspar Kirstein Nielsen 1 , Stefano Dallolio 1 , Anders Smith 1 , Christian Bahl 1 Show Abstract
1 , TU Denmark, Roskilde Denmark
The demand for high cooling power devices with a high efficiency is a challenge for electricity consuming devices such as refrigerators, air conditioners and heat pumps. For this reason, a significant amount of research on alternative refrigeration technologies is being done around the world. DTU Energy has been active in this field for more than 10 years, in particular within magnetic refrigeration and more recently on elastocaloric devices. Alongside the work on magnetocaloric devices we have built up competences in the design of permanent magnet assemblies, regenerator modelling for both magneto- and elastocalorics as well as materials characterisation. We aim to develop high performance devices with a firm control of all of the involved parameters. The similarity of the caloric technologies allows us to utilise the knowledge gained in one to further the advances of the others. In this talk I will present the recent activities of the group in this area demonstrating a large temperature span achieved in both caloric technologies while achieving a high efficiency.
4:00 PM - *ES8.5.06
Small Scale Elastocaloric Cooling by SMA Films
Manfred Kohl 1 , Hinnerk Ossmer 1 , Florian Bruederlin 1 , Frank Wendler 1 , Christoph Chluba 2 , Lars Bumke 2 , Eckhard Quandt 2 Show Abstract
1 , Karlsruhe Institute of Technology, Karlsruhe Germany, 2 Institute for Material Science, Christian Albrecht University Kiel, Kiel Germany
The elastocaloric effect associated with the stress-induced first order phase transformation in pseudoelastic shape memory alloys (SMAs) is of special interest for cooling applications. NiTi-based alloys, for instance, exhibit a unique combination of large latent heat in the order of 24 J/g, large transformation strain of 8 % and good scalability on miniaturization. Elastocaloric cooling in film devices is expected to enable fast heat transfer, high cycling frequencies as well as tunable temperature change. Target applications are on a small scale including microelectronics, micro-electro-mechanical systems (MEMS) and lab-on-chip systems, while larger scales are envisioned by massive parallelization.
Concerning materials research, major challenges are the optimization of effect size and long-term fatigue properties. Several material systems have been identified that might fulfill these criteria. Among them are Ti-rich Ti-Ni-Cu-based films that have been demonstrated to exhibit ultra-low fatigue properties. Local strain and temperature profiles of the films are investigated during tensile load cycling with respect to strain, strain-rate and cycle number by in-situ digital image correlation (DIC) and infrared thermography. DIC measurements show that phase transformation occurs by reversible strain rate-dependent formation and propagation of strain bands. This behavior is correlated with the evolution of local temperature profiles revealing elastocaloric cooling by -12 K in adiabatic case. The corresponding material’s coefficient of performance (COP) is determined to be 15. The measurements are complemented by phase field simulations that predict tilt angle and rate dependence of band formation and evolution.
Major challenges in development of elastocaloric microcooling devices are the engineering of thermal interfaces for efficient heat transfer as well as force recovery to enhance the COP on the system level. Several generations of demonstrators will be presented that address the various design issues. First-of-its-kind demonstrators making use of SMA bridge devices reach a temperature span of almost 10 K after 100 cycles, while the COP reaches 10% of Carnot efficiency. Corresponding heat transfer processes in the system are accurately described using a lumped element model. Recent developments of regeneration devices using thin films with chemical composition gradients will be presented to further enhance the temperature span.
4:30 PM - *ES8.5.07
Compression-Based Elastocaloric Materials and Cooling Devices
Ichiro Takeuchi 1 Show Abstract
1 , University of Maryland, College Park, Maryland, United States
We are developing prototypes of elastocaloric cooling systems using mechanisms based on compression of shape memory alloys. We are compressing bundles of NiTi tubes while heat exchange fluid flows through the tubes. A key component is a heat recovery system implemented in order to maximize the efficiency of the heat exchange. We have observed cooling deltaT of 4.5 K at 70 W, as directly measured in cooled water. A latest prototype was designed to deliver 400 W. We have demonstrated that when properly loaded, shape memory alloy tubes can survive up to at least ~ 0.3 million cycles without any degradation in cooling capacity. We are also carrying out combinatorial investigation of ternary and quaternary alloys to identify new compositions with enhanced latent heat with reduced critical stress. Our materials optimization processes include developing understanding of the effect of atomic structure and microstructure on the latent heat and fatigue. This work is performed in collaboration with S. Qian, J. Muehlbauer, R. Radermacher, Y. Hwang, J. Ling, H. Hou, N. Hasan, D. Catalini, and J. Cui. This project is funded by DOE ARPA-E and DOE EERE CaloriCool.
Xavier Moya, University of Cambridge
Christian Bahl, Technical University of Denmark
Jun Cui, Ames Laboratory, Iowa State University
Emmanuel Defay, Luxembourg Institute of Science and Technology
aixACCT Systems GmbH
ES8.6: Mechanocalorics, Modeling and Materials
Thursday AM, April 20, 2017
PCC North, 200 Level, Room 226 B
9:00 AM - *ES8.6.01
Caloric Effects from Direct First-Principles Simulations
Inna Ponomareva 1 Show Abstract
1 , University of South Florida, Tampa, Florida, United States
Simulations of caloric effects at the atomistic level is a challenging task as it requires computations at finite temperature and under applied external fields. As a result standard computational tools, such as Density Functional Theory methods, are not well suited for simulations of caloric responses which slows down the progress in the atomistic understanding of the caloric effects. To overcome this challenge we develop a computational methodology that combines classical simulations (such as adiabatic Monte Carlo and Molecular Dynamics) with accurate first-principles-based potentials. Application of such novel methodology to study various caloric effects leads to the prediction of unusual caloric responses and other related properties.
One such example is the caloric effects in antiferroelectrics. Antiferroelectrics are the antipolar counterparts of ferroelectrics and do not exhibit spontaneous polarization. Application of our computational methodology to the study of electrocaloric effect in antiferroelectric PbZrO3 revealed that the electrocaloric temperature change in such material exhibit scaling behavior similar to the one reported for magnetic materials . Another unique feature of antifferroelectric is their strong electromechanical coupling. Our simulations predict that such coupling gives origin to highly tunable piezocaloric effect in antiferroelectrics .
Interestingly, while the most anticipated technological application of caloric materials is for solid-state refrigeration, there seems to be other possibilities that so far have been overlooked. One example is the potential use of caloric effects to couple magnetization and polarization in multiferroics. We use the atomistic simulations to demonstrate this new type of magnetoelectric coupling in BiFeO3  and then review some multiferroic heterostructures that could exhibit enhanced magnetoelectric coupling.
Finally, we take advantage of atomistic simulations and explore rather unconventional strategy to screen caloric materials. Namely, we look for materials that have moderate caloric response but allow application of large external fields. Unexpectedly, we find that carbon nanotubes and graphene could be excellent candidates for giant elastocaloric effect as they allow application of extremely high stress. Our simulations predict that an elastocaloric effect of up to 30 K could be obtained from carbon nanotubes .
1. S. Lisenkov, B.K. Mani, E. Glazkova, C.W. Miller and I. Ponomareva
Sci. Rep. 6, 19590 (2016);
2. S. Lisenkov, B. K. Mani, J. Cuozzo and I. Ponomareva
Phys. Rev. B, 93, 064108 (2016);
3. C.-M. Chang, B. K. Mani, S. Lisenkov, and I. Ponomareva
Phys. Rev. Lett. 114, 177205 (2015);
4. S. Lisenkov, Ryan Herchig, Satyanarayan Patel, Rahul Vaish, J. Cuozzo, and I. Ponomareva, Nano Lett. (2016).
9:30 AM - *ES8.6.02
Elastocaloric Effect in Natural Rubber and P(VDF-TrFE-CFTE) Terpolymer
Gael Sebald 1 2 , Zhongjian Xie 2 , Yukihiro Yoshida 2 , Kaori Yuse 2 , Daniel Guyomar 2 , Jean-Fabien Capsal 2 Show Abstract
1 , ELyTMaX - Université de Lyon - CNRS - Tohoku University, Sendai Japan, 2 LGEF, Université de Lyon, INSA-Lyon, Lyon France
In the framework of research on alternative cooling technologies using caloric materials, elastocaloric materials are a promising solution, like shape memory alloys (SMA) or natural rubber (NR). The elastocaloric properties of natural rubber are presented in this work: elastocaloric effect characterization, discussion about indirect/direct characterization correspondence, effect of a pre-strain, physical modelling and fatigue study. Firstly, the properties of NR are presented. For example, the adiabatic temperature change reaches 8° upon a strain level of 6 on a mechanically soft natural rubber sample. Indirect and direct characterization being used in the case of other caloric couplings, it is tested here in the case of NR elastocaloric effect. The directly measured temperature change upon deformation (elastocaloric effect) of natural rubber (NR) was thus compared with indirect method, which is deduced from the derivative of the stress with respect to temperature. A tentative model is proposed for highlighting the physical insights of the eCE in this material. It is especially shown that the dynamics of the crystallization strongly influence the mechanical properties whereas elastocaloric properties remain weakly affected. Finally, repetitive stretching are tested for determining the fatigue properties of the natural rubber. It is shown that the material withstand up to 170,000 cycles under strain from 2 to 5 without any degradation of elastocaloric properties. Pursuing the search for suitable materials for elastocaloric cooling, PVDF-TrFE-CFTE terpolymer, known to be an excellent electrocaloric material, is finally tested for its elastocaloric properties. The effect is lower than for NR (with adiabatic temperature around 2°), but is obtained for much lower strain level (0.1). The origin of the effect is shown to be moreover related to the elastic entropy only by internal energy considerations, contrary to NR where the main contribution to the entropy change is the strain-induced crystallization latent heat.
10:30 AM - ES8.6.03
Giant Barocaloric Effects in Ferroelectrics
Xavier Moya 1 Show Abstract
1 , University of Cambridge, Cambridge United Kingdom
P. Lloveras1, E. Stern-Taulats2, W. Li3, M. Barrio1, J.-Ll. Tamarit1, A. Planes2, Ll. Mañosa2, N. D. Mathur3 and X. Moya3
1Departament de Física i Enginyeria Nuclear, ETSEIB, Universitat Politècnica de Catalunya, Diagonal 647, Barcelona, 08028 Catalonia, Spain
2Facultat de Física, Departament d’Estructura i Constituents de la Matèria, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Catalonia, Spain
3Department of Materials Science, University of Cambridge, Cambridge, CB3 0FS, UK
Barocaloric materials driven by hydrostatic pressure are currently being considered for cooling applications, following the observation of giant barocaloric effects in a small range of magnetic materials that are relatively expensive. Here I will present pressure-dependent calorimetry data to demonstrate giant barocaloric effects in a number of ferroelectric materials that are made of cheap abundant elements.
10:45 AM - ES8.6.04
Effect of Pressure on Spin Crossover Compounds for Barocaloric Applications
Steven Vallone 1 2 , Antonio dos Santos 3 , Jamie Molaison 3 , Malcolm Halcrow 4 , Karl Sandeman 1 2 Show Abstract
1 , Brooklyn College of The City University of New York, Brooklyn, New York, United States, 2 Physics Program, The Graduate Center, CUNY, New York, New York, United States, 3 Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 4 School of Chemistry, University of Leeds, Leeds United Kingdom
Spin crossover occurs in compounds where the crystal field splitting of d-orbitals associated with a magnetic moment is of the order of kBT. The effect is typically most observed in octahedrally coordinated complexes of Fe in e.g. d5 or d6 electronic configurations. As a result, a change of state from low spin (LS) to high spin (HS) can occur at the so-called spin crossover temperature, TSCO. The low temperature state breaks Hund’s rules. Crucially for caloric applications, the change of state from LS to HS can be either continuous or first order, and it can occur at temperatures up to and beyond room temperature. Since SCO compounds are paramagnets, the largest caloric effects will be barocaloric (triggered by applied pressure) rather than magnetocaloric effects brought about by an applied magnetic field .
In magnetocaloric materials research, an essential point of comparison has been the caloric output of first order and second order materials. First order materials yield a larger entropic output at a single temperature, but offer a reduced temperature response window, and may possess hysteresis, which is a source of loss in application. Hence there has been interest in (tri)criticality, or tunable magnetoelastic coupling (termed "cooperativity" by the SCO community). In this presentation, we use neutron scattering to examine the evolution of the structure of a first order SCO compound with applied pressure. In particular, we examine sub-1 kbar pressures and their effect on SCO transition hysteresis.
 K.G. Sandeman, APL Materials in press doi: 10.1063/1.4967282
 K.S. Murray, in Spin-Crossover Materials: Properties and Applications, edited by M.A. Halcrow, 1st ed. (John Wiley & Sons Ltd, 2013), pp. 1–54.
11:00 AM - ES8.6.05
Large Caloric Effects in Soft Materials
Zdravko Kutnjak 1 , Trcek Maja 1 , Marta Lavric 1 , George Cordoyiannis 1 , Bostjan Zalar 1 , Qiming Zhang 2 Show Abstract
1 , Jozef Stefan Institute, Ljubljana Slovenia, 2 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, United States
Materials with large caloric effect have the promise of realizing solid state refrigeration which is more efficient and environmentally friendly compared to current techniques . A review of recent direct measurements of the large electrocaloric effect in liquid crystalline materials [2,3] and large elastocaloric effect in liquid crystal elastomers will be given. In liquid crystalline materials and mixtures of liquid crystals with functionalized nanoparticles the electrocaloric effect exceeding 8 K was found in the vicinity of the isotropic to smectic phase transition. Direct measurements indicate that the elastocaloric response of similar magnitude can be found in main-chain liquid crystalline elastomers . Both soft materials can play significant role as active cooling elements and parts of thermal diodes or regeneration material in development of new cooling devices.  Z. Kutnjak., B. Rozic. and R. Pirc., Electrocaloric Effect: Theory, Measurements, and Applications (Wiley Encyclopedia of Electrical and Electronics Engineering) 2015, p. 1-19.  I. Lelidis and G. Durand. Phys. Rev. Lett. 1996, 76, p 1868.  X.-S. Qian et al., Adv. Funct. Mater. 23, 2894 (2013).  A. Lebar, G. Cordoyiannis, Z. Kutnjak, B. Zalar, Adv. Polym. Sci. 250, 147 (2012).
11:15 AM - ES8.6.06
Infra-Red Imaging of Elastocaloric Polymers
Alex Avramenko 1 , Xavier Moya 1 Show Abstract
1 , University of Cambridge, Cambridge United Kingdom
A. Avramenko, M. Dilshad and X. Moya
Department of Materials Science, University of Cambridge, Cambridge CB3 0FS, UK
Large elastocaloric effects driven by applied uniaxial stress have been demonstrated in metallic alloys and polymers . Elastocaloric quantities are typically obtained via the thermodynamic analysis of temperature-dependent stress-strain measurements, or via contact thermometry. Here, we investigate elastocaloric effects in polymers using an infra-red camera that permits the study of inhomogeneity and heat flow.
 X. Moya, S. Kar-Narayan, and N. D. Mathur, Nat. Mater. 13, 439 (2014).
ES8.7: Magnetocaloric Materials
Thursday PM, April 20, 2017
PCC North, 200 Level, Room 226 B
1:30 PM - *ES8.7.01
Entropic Features of the Electronic Phase Owing to Multiple Degrees of Freedom of Electron
Asaya Fujita 1 Show Abstract
1 , AIST Chubu, Aichi Japan
Development of caloric materials is one of the key factors for realization of the solid-state refrigeration technique. In solid-state substances, thier entropic characteristics are mainly provided by phonons in the conventional frameworks such as a heat-sink device. Meanwhile, recent demands on construction of the heat-pump cycle focus on the solid-state phase transitions controlled not only by thermal change but also by application of external fields such as magnetic, electric or strain fields. In this regards, the transition of “electronic phase” are invaluable phenomena owing to their latent heat generation, together with their controllable feature against the external fields.
From thermodynamic relation, the latent heat generation at the first-order phase transition caused by the conversion between the internal energy (enthalpy) gain at the low-temperature phase and the free energy (entropy) gain at the high-temperature phase. In the electronic phase affected by the electron-correlation, a selection in kind of degree of freedom by electron governs an enthalpy-entropy conversion behavior. For instance, trigger of the exchange splitting in 3d bands in the itinerant-electron ferromagnetic state in La(Fe,Si)13 is an energy gain brought about by reduction of electron correlation. In this case, a local correlation between an individual pair of 3d electrons is small, while sum-up of correlations for one electron from other all electrons in a system collectively affect the total energy because of “itinerancy”. Meanwhile, in the paramagnetic state, the disordered local moment (DLM) state appears instead of the Pauli paramagnetic state. In the DLM state, a certain weakening of local correlation occurs owing to local spin polarization, while random fluctuations of the DLM earns a large entropy, which is a driving force of the first-order transition to the paramagnetic state. From the fact that the increase of the itinerant character apart from the DLM state tends to blur the first-order transition, a larger entropic gain seems to be earned by the DLM state compared to the randomness of up/down spin direction in the Pauli paramagnetic state.
Another unique example of the caloric phenomenon related to the degree of freedom of electron is a large latent heat at the Mott-type metal-insulator transitions. In this case, strong electron correlation forbids forming metallic band structure, resulting in an insulating ground state. The atomic bond at the insulating ground state is close to a covalent-type one in which degeneracy of 3d band is largely disentangled by crystalline fields, and two electrons forms spin-singlet (total S=0) state. In other words, orbital selectivity quenches both charge and spin fluctuations. Meanwhile, the metallic state emerges at the high-temperature state. This change does not come from a weakening of correlations, but from the entropy gain by (melting of) the charge and spin fluctuations at the high-temperature state.
2:00 PM - *ES8.7.02
Large Magnetization and Reversible Magnetocaloric Effect at the Second-Order Magnetic Phase Transition in Heusler Materials
Luana Caron 1 , Sanjay Singh 1 , Sunil Wilfred D'Souza 1 , Tina Fichtner 1 , Giacomo Porcari 2 , Simone Fabbrici 3 , Chandra Shekhar 1 , Stanislav Chadov 1 , Massimo Solzi 2 , Claudia Felser 1 Show Abstract
1 , Max Planck Institute for Chemical Physics of Solids, Dresden Germany, 2 , Parma University, Parma Italy, 3 , IMEM-CNR, Parma Italy
Since the observation of a giant magnetocaloric effect (MCE) in Gd5Ge2Si2, the search for materials for MCE-based applications has been focused on compounds showing first order phase transitions. However, the practical application of giant MCE materials is hindered by the nature of the transition itself. In order to drive a first order phase transition, energy is spent to overcome the energy barrier between different states. This energy loss leads to irreversibilities in both temperature and entropy changes in addition to discontinuous structural changes which cause physical instability. In this work we explore theoretically and experimentally how to obtain high magnetic moments in cubic Ni2(Mn,X)2 X= Ga, In, Sn Heusler alloys. Our aim is to design Heusler compounds presenting a combination of high ground state moment and a fully reversible second order phase transition for magnetocaloric cooling applications. Using ab initio calculations we have determined the exchange interactions and magnetic moments of these alloys in the cubic structure as to maximize the net saturation magnetization. As a proof of concept we present the magnetic and MCE properties of the Ni2Mn1.4In0.6 compound which presents a calculated and measured saturation moment comparable to that of Gd.
2:30 PM - *ES8.7.03
A Search for Advanced Magnetic Refrigerant Materials in the Heusler Alloy System
Francis Johnson 1 Show Abstract
1 , GE Global Research, Niskayuna, New York, United States
Magnetic refrigeration is an alternative to vapor compression technology that has long held the promise of increased cooling system efficiency. The first part of this presentation will review the material and system parameters needed to design a practical magnetic refrigerator. The engineering principles reside at the intersection of material physics, heat transfer phenomena, and both chemical and mechanical thermodynamics. Magnetic refrigerant materials and permanent magnets comprise the active components of most systems specified for residential and commercial markets. To be useful, the refrigerant materials must display a reversible solid-state phase transformation with a large magnetocaloric effect within the magnetic field supplied by the magnets. The field and temperature dependence of the magnetocaloric phase transformations may be represented on a magnetic phase diagram. The irreversibility of the phase transition, quantified as hysteresis, will determine if a usable magnetocaloric effect can be harvested in the available magnetic field and temperature ranges.
The second part will present an effort to design new magnetic refrigerant materials led by GE Global Research from 2011 to 2013. Four groups of Heusler alloys were explored to determine their potential as magnetic refrigerant materials. The Heusler alloys are intermetallic compounds that exhibit a rich variety of magnetic and structural phase transitions. In this study, nickel-manganese based Heusler alloys were selected due to magnetostructural transitions available near room temperature. Compositions displaying both normal and inverse magnetocaloric effects were studied, and the geometric non-linear theory of martensite identified low-hysteresis compositions. CALPHAD methods were used to predict solidus and liquidus temperatures and select homogenization temperatures in the disordered bcc phase fields. A high throughput arc-melting technique produced 180 discrete compositions for magnetic and structural characterization. Multistep heat treatments improved control of phase transition temperatures. Compositions with transition temperatures from -23 °C to 77 °C were identified. Control of the transition temperature to within ±1 °C was demonstrated. A maximum magnetic field sensitivity of 7°C/Tesla was observed. The maximum adiabatic ΔT observed was 2 °C at 1.5 Tesla, but the minimum hysteresis was 6 °C, preventing these compositions from being usable as magnetic refrigerants. Compositions that were predicted to have lower hysteresis were unable to be made by available methods, holding out the possibility that advanced manufacturing techniques might yield lower hysteresis.
3:30 PM - ES8.7.04
Controlling the Magnetic Properties of La(Fe,Mn,Si)13 and Its Hydrides with Pressure
Henrique Neves Bez 1 , Edmund Lovell 2 , David Boldrin 2 , Kaspar Nielsen 3 , Anders Smith 3 , Christian Bahl 3 , Lesley Cohen 2 Show Abstract
1 , Ames Laboratory, Ames, Iowa, United States, 2 , Imperial College London, London United Kingdom, 3 , Technical University of Denmark, Lyngby Denmark
La(Fe,Mn,Si)13Hz is one of the most promising and industrially available magnetocaloric materials. However, its application in a magnetic cooling device still faces challenges, which include irreversible energy loss through hysteresis. La(Fe,Mn,Si)13Hz alloys present a large magnetocaloric effect with a Curie temperature, TC, that is tunable by interstitial atoms such as H and C, by adjusting the Fe/Mn/Si ratio or by hydrostatic pressure. Several studies have examined the influence of hydrostatic pressure on La(Fe,Si)13 and its hydrides, although taken together the results are not entirely consistent. Here, we present a systematic study of the effect of applied hydrostatic pressure on the magnetic properties of La(Fe,Mn,Si)13 and its hydrides. Different trends are observed for dehydrogenated and hydrogenated samples. We find that the TC in the dehydrogenated sample is significantly more sensitive to application of hydrostatic pressure compared to its hydrogenated counterpart, implying a different compressibility or a difference in the magneto-elastic coupling strength between the two samples. In addition, the entropy change is modified differently by pressure in each case: the dehydrogenated sample entropy change decreases and broadens significantly, while the entropy change in the hydride sample is significantly less affected. This is further observed when analyzing the Clapeyron equation: Δs=ΔM(dTC/dH)-1, where s is entropy, M is magnetization and H is magnetic field. We observe that (dTC/dH)-1 decreases by a factor of three with pressure up to 1GPa for the dehydrogenated sample, suggesting a weakening of first order character, whilst it remains rather constant in the hydrogenated sample. However, when analysing the H-T phase diagrams under different pressures both samples present an increase in the thermal hysteresis. Finally we propose a method to decrease the hysteretic losses in the magnetization cycle by more than 90%, by employing application of pressure in part of the refrigeration cycle, which we denote as dynamic pressure control.
3:45 PM - ES8.7.05
Phase Transition Growth Dynamics in La(Fe,Mn,Si)13 Magnetocaloric Compounds
Edmund Lovell 1 , Milan Bratko 1 , David Caplin 1 , Lesley Cohen 1 Show Abstract
1 , Imperial College London, London United Kingdom
La(Fe,Si)13-based magnetocaloric compounds are promising contenders for use in environmentally friendly and energy-efficient solid-state magnetic cooling. Material systems for such use require a magnetic phase transition which can be induced by relatively small magnetic fields (<1-2 T: within the range of permanent magnets) concurrent with a large magnetic entropy change and a large adiabatic temperature change. Those exhibiting a phase transition of first-order type often fulfil these criteria and La(Fe,Si)13 is further attractive within this category due to the wide tunability of its working temperature in response to compositional variations, and its relatively small intrinsic hysteresis (which results in reduced energy losses within a cyclic cooling device) . Nevertheless, La(Fe,Si)13 is known to demonstrate dynamic growth characteristics during the magnetic phase transition, on the timescale of 10s to 100s of seconds. Specific manifestations include a dependence on the rate of change of applied driving field, relaxation between metastable states , and so-called “avalanche-like” periods of accelerated growth between metastable mixed states indicative of a complicated free energy landscape on the local scale . These dynamic effects impact the transformation kinetics at field rates that are similar to the expected cycling frequencies in refrigeration applications. Therefore, achieving a better understanding of the mechanisms responsible for these effects is important and timely. Here we study compounds of Mn-doped La(Fe,Si)13 using magnetometry and a calorimetric method which can separate the contributions from heat capacity and latent heat at the transition. A field rate independent dynamic signature of separate transition events is observed in the latent heat, which progresses faster with improved thermal coupling to the surroundings and which we show has no impact on the magnitude of the total intrinsic heat release, and is also dependent on temperature. We explore this dynamic aspect in terms of thermal linkage, microstructure and the strength of first-order character.
 A. Smith, C. R. H. Bahl, R. Bjørk, K. Engelbrecht, K. K. Nielsen, N. Pryds, Adv. Energy Mater. 2, 1288-1318 (2012)
 E. Lovell, A. M. Pereira, A. D. Caplin, J. Lyubina, L. F. Cohen, Adv. Energy Mater. 5, 1401639 (2015)
 M. Kuepferling, C. Bennati, F. Laviano, G. Ghigo, V. Basso, J. Appl. Phys. 115, 17A925 (2014)
4:00 PM - ES8.7.06
Structural and Magnetocaloric Properties of Ball Milled LaFe13-xSix(H,C)y
Lotfi Bessais 1 , Mathieu Phejar 1 , Valerie Paul Boncour 1 Show Abstract
1 , CNRS, Thiais France
LaFe13-xSix compounds display a giant magnetocaloric effect near 200 K. The insertion of light elements (H, C) is used to improve the Curie temperature near ambient temperature for magnetic refrigeration applications. We have developed a synthesis method with a short annealing treatment compared to classical melting techniques .
The parent intermetallic alloys were synthesized by high energy ball milling. The insertion of H atoms was carried out using a Sievert apparatus and the carbon atom was inserted by solid/solid reaction. Moreover, structural and magnetic results were carried out by neutron diffraction and Mössbauer spectroscopy for H contents (y = 0.7, 1.5) and C content (y = 0.7).
The cell parameter and the Fe magnetic moments versus temperature are determined. The misunderstanding on interstitial site is clarified. The magnetovolumic effect on the Curie temperature is explained by combination of the structural and magnetic properties. The advantages and drawbacks of each type of element insertion are discussed.
 M. Phejar, V. Paul-Boncour and L. Bessais Intermetallics 18 (2016) 2301-2307.
4:15 PM - ES8.7.07
Inverse Magnetocaloric Effect in Metamagnetic Ni-Mn-In-Based Alloys in High Magnetic Fields
Sudip Pandey 1 , Yury Koshkid’ko 2 , Abdiel Quetz 1 , Anil Aryal 1 , Igor Dubenko 1 , Jacek Cwik 2 , Elvina Dilmieva 2 , Alexander Granovsky 3 , Erkki Lahderanta 4 , Arkady Zhukov 5 , Shane Stadler 6 , Naushad Ali 1 Show Abstract
1 , Southern Illinois University, Carbondale, Illinois, United States, 2 , International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw Poland, 3 , Lomonosov Moscow State University, Moscow Russian Federation, 4 , Lappeenranta University of Technology, Lappeenranta Finland, 5 , Departamento de Física de Materiales, Fac. Químicas, UPV/EHU, Bilbao Spain, 6 , Louisiana State University, Baton Rouge, Louisiana, United States
Magnetocaloric effects (MCE) in Ni50Mn35In15, Ni50.2Mn34.85In14.95, and Ni50Mn35In14.25B0.75 Heusler alloys have been studied through direct measurements of the adiabatic temperature change (ΔTad) using the extraction method for magnetic field changes up to 14 T. Both the ΔTad and the entropy changes (ΔSM) increase as the martensitic transition approaches the Curie temperature of the austenitic phase. The ΔTad increases up to a maximum value of 6K with field and saturates at high fields ΔH = 7 T. The influence of the rate of change of the magnetic field and the rate of heating to the initial temperature before applying field on the ΔTad of Ni50Mn35In14.25B0.75 has been studied. It has been shown that increasing the heating rate from 6 to 22 K/min results in an increase of ΔTad by about 40% for ΔH=10 T. The effect is discussed in the terms of the influence of the heating rate on the austenitic phase nucleation. The obtained results on critical magnetic fields for MCE saturation and kinetic effects are applicable to any other system displaying MCE at first-order magnetostructural phase transitions.
This work was supported by the Office of Basic Energy Sciences, Material Science Division of the U.S. Department of Energy, DOE Grant No. DE-FG02-06ER46291 (SIU) and DE-FG02-13ER46946 (LSU). The authors from Lomonosov Moscow State University acknowledge support from the Russian Foundation for Basic Research (Grant No.15-02-01976). The authors from the International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw acknowledge support from project No.146-MAGNES of the ERA.Net RUS Plus initiative of the EU 7th Framework Program.
4:30 PM - ES8.7.08
Magnetocaloric Improvements in Doped Heusler Alloys
Michael McLeod 1 , Bhaskar Majumdar 1 , Zafer Targut 2 Show Abstract
1 , New Mexico Tech, Socorro, New Mexico, United States, 2 , Air Force Research Laboratory, Dayton, Ohio, United States
Magnetocaloric materials have gained significant interest as an environment friendly and efficient refrigeration technology. We have been working on Heusler alloys, primarily the Ni-Mn-Ga system for improved magnetocaloric effect (MCE). We have observed large MCE increase in stress assisted thermally cycled samples and demonstrated that one primary mechanism is texture change such that the easy magnetization axis is aligned along the magnetic field. More recently we have observed volumetric decrease as well as anisotropy changes due to stressed cycling. The influence of these parameters on magnetization and MCE behavior will be discussed. We have also utilized substitutional Al dopant in place of Ga for optimizing atomic distances and exchange interactions in an effort to bring magnetostrucutural transformation closer to RT while retaining high MCE. The results and mechanisms will be presented. If time permits, we will also discuss doping in the metamagnetic Ni-Mn-Sn system where our focus is on interstitial dopants for improved MCE.
4:45 PM - ES8.7.09
Direct Measurement of Magnetocaloric Effect in Ni2+xMn1-xGa (0.18 ≤ x ≤ 0.27) with Coupled Magnetostructural Phase Transition
Vladimir Khovaylo 1 , Konstantin Skokov 2 , Sergey Taskaev 3 Show Abstract
1 , National University of Science and Technology, Moscow Russian Federation, 2 , Technical University Darmstadt, Darmstadt Germany, 3 , Chelyabinsk State University, Chelyabinsk Russian Federation
A great effort has been aimed during last decades at the development of materials suitable for energy saving solid-state magnetic refrigeration, especially for room-temperature applications such as air-conditions and refrigerators. Intensive studies of various intermetallic systems revealed that the largest magnetocaloric is observed in compounds undergoing a first-order magnetic phase transition. The enhanced magnetocaloric effect in such materials has been proved to be due to a contribution from the elastic subsystem.
In Ni2+xMn1-xGa, martensitic transformation temperature Tm tends to increase and Curie temperature TC tends to decrease with deviation from the stoichiometry until they merge in a Ni2.18Mn0.82Ga composition. Both the transitions are coupled in rather an extended interval of Ni2+xMn1-xGa compositions, from x = 0.18 to x = 0.27. Here we report on direct measurement of magnetocaloric effect and its compositional dependence in Ni2+xMn1-xGa with coupled magnetostructural phase transition. Experimental results obtained revealed that adiabatic temperature change DT is the largest in the alloys with x = 0.18 – 0.20. Magnetocaloric effect in the alloys with a higher Ni excess was found to be considerably smaller. This tendency in the compositional dependence of DT is attributed to the fact that with increasing Ni excess x, a simultaneous decrease in magnetization saturation and in the lattice entropy change at martensitic transformation temperature is observed.
ES8.8: Poster Session
Thursday PM, April 20, 2017
Sheraton, Third Level, Phoenix Ballroom
8:00 PM - ES8.8.01
Giant Magnetocaloric Effect Induced by Reemergence of Magnetostructural Coupling in Si-Doped Mn0.95CoGe Compounds
Hu Zhang 1 , YaWei Li 1 , Kun Tao 1 , YiXu Wang 1 , MeiLing Wu 1 , Yi Long 1 Show Abstract
1 , School of Materials Science and Engineering, University of Science and Technology of Beijing, Beijing China
It has been reported that the martensitic structural transformation temperature (Tstr) can be lowered and even depressed by the Mn vacancy in MnCoGe-based alloys. In present work, the structural transformation is tuned to reappear and the Tstr increases significantly by substituting Si for Ge in Mn0.95CoGe system, and thus the magnetostructural transition from paramagnetic Ni2In-type phase to ferromagnetic TiNiSi-type phase is again realized around room temperature. Meanwhile, the working temperature window is enhanced to be 22 % wider than that of Mn1-xCoGe system. The history-dependent phase transitions have been discussed by measuring the M-H curves in different processes. The Mn0.95CoGe0.9Si0.1 experiences a forward martensitic transition in loop process, and then a field-induced metamagnetic transition (FIMT) with large magnetic hysteresis can be observed around Tstrcooling. On the other hand, a reverse martensitic transition is observed in standard process, and the FIMT is depressed by thermal disturbance at higher temperatures. Large MCE is obtained due to the reemergence of magnetostructural transition, e.g., the maximum -ΔSM is 15.0 J/kg K for a relatively low field change of 2 T, which is larger than those of Mn1-xCoGe system and some other typical magnetocaloric materials in the similar temperature range. The comprehensive advantages including giant low-field MCE, wide working temperature range, and lower cost of Si than Ge, suggest that Mn0.95CoGe1-xSix compounds could be promising materials for room temperature magnetic refrigeration.
8:00 PM - ES8.8.02
Magnetocaloric Properties of HoNi2 Melt-Spun Ribbons
Cesar Fidel Sanchez-Valdes 1 , Pablo Jesus Ibarra-Gaytan 2 , Jose Luis Sanchez Llamazares 2 , Pablo Alvarez-Alonso 3 Show Abstract
1 , División Multidisciplinaria, Ciudad Universitaria, Universidad Autónoma de Ciudad Juárez (UACJ), Ciudad Juárez, Chihuahua, Mexico, 2 , Instituto Potosino de Investigación Científica y Tecnológica A.C., San Luis Potosí, S.L.P., Mexico, 3 , Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), Leioa, Vasque Country, Spain
Theoretical and experimental studies show that the binary Laves phases RNi2 with the heavy rare-earth elements R= Tb, Dy, Ho, Er, are attractive magnetic refrigerants in the cryogenic temperature range . Apart from their large saturation magnetization, which give rise to a large magnetocaloric effect, some of these compounds exhibit a peculiar anisotropic magnetization behaviour that may lead to enhanced magnetocaloric properties along a certain notable crystallographic direction. This contribution focuses on the intermetallic binary phase HoNi2. Instead the conventional synthesis procedure, i.e., arc or RF melting followed by a long-term thermal annealing, we have fabricated microcrystalline melt-spun ribbons of average thickness 32-35 µm of this binary Laves phase and studied their phase constitution and magnetocaloric properties by X-ray diffraction, SEM, magnetization and heat capacity measurements. Samples were produced from bulk arc melted alloys previously obtained from highly pure elements (≥ 99.9 %), whereas melt spinning process was carried out using the model SC Edmund Bühler melt spinner system under a highly pure Ar atmosphere at a linear speed of the rotating copper wheel linear of 20 ms-1. As-prepared ribbons are single phase; they crystallize in the cubic MgCu2-type crystal structure of the Laves phases (C15; space group Fd-3m). EDS analyses confirmed their 1:2 average elemental composition. A Curie temperature TC of 14 ± 1 K has been estimated from the low-field M(T) curve (5 mT), which agrees with the reported for bulk alloys [2-6]. The saturation magnetization at 2 K and 5 T is 162 ± 2 Am2kg-1. Magnetic entropy change curves obtained from magnetization and heat capacity measurements applying the magnetic field along the ribbon length are in good agreement. For a magnetic field change of 5 T (2 T), the produced ribbons show a maximum magnetic entropy change |ΔSMmax| of 27-31 (17-18) Jkg-1K-1 and an adiabatic temperature change of 12.6 (6.7) K. The results are compared with calculated and experimental values reported for bulk alloys.
Work financially supported by Laboratorio Nacional de Investigaciones en Nanociencias y Nanotecnología (LINAN, IPICyT). The technical support received from Dr. G. J. Labrada-Delgado and M.Sc. B.A. Rivera-Escoto during SEM and XRD observations, respectively, is recognized. P. J. Ibarra-Gaytán thanks CONACyT for supporting his Ph.D. studies.
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8:00 PM - ES8.8.03
Effect of Annealing on the Magnetic, Thermal, and Magnetocaloric Properties of B Doped Ni-Mn-In Ribbons
Sudip Pandey 1 , Abdiel Quetz 1 , Anil Aryal 1 , Pablo Jesus Ibarra-Gaytan 2 , Igor Dubenko 1 , Dipanjan Mazumdar 1 , Jose Luis Sanchez Llamazares 2 , Shane Stadler 3 , Naushad Ali 1 Show Abstract
1 Physics, Southern Illinois University, Carbondale, Illinois, United States, 2 , Instituto Potosino de Investigación Cientifica y Tecnológica , San Luis Mexico, 3 Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana, United States
The structural, thermal, magnetic, and magnetocaloric properties of Ni50Mn35In14.5B0.5 melt-spun ribbons have been investigated using room-temperature x-ray diffraction (XRD), differential scanning calorimetry (DSC), and magnetization measurements. Magnetic and structural transitions were found to coincide in temperature leading to large magnetocaloric effects associated with the first-order magnetostructural phase transition. In comparison to the bulk and as-spun ribbons, both the martensitic transition temperature (TM) and Curie temperature (TC) shifted to lower temperatures on annealed Ni50Mn35In14.5B0.5 ribbons. Significant increase in magnetocaloric effect has been observed between the as-spun and the annealed ribbons. A comparison of magnetic properties and magnetocaloric effects in Ni50Mn35In14.5B0.5 as-spun ribbons, bulk, and annealed ribbons have been shown in detail. The roles of the magnetic and structural changes on the transition temperatures of the ribbons are discussed.
This work was supported by the Office of Basic Energy Sciences, Material Science Division of the U.S. Department of Energy, DOE Grant No. DE-FG02-06ER46291 (SIU) and DE-FG02-13ER46946 (LSU). The authors acknowledge financial support received from Laboratorio Nacional de Investigaciones en Nanociencias y Nanotecnología (LINAN, IPICyT) and CONACyT, Mexico (Grant No. 156932).
8:00 PM - ES8.8.04
Multi-Regime Non-Linear Pyroelectric Energy Harvesting in Thin Films
Brendan Hanrahan 1 , Andrew Smith 2 , Hamidreza Khassaf 3 , S. Pamir Alpay 3 Show Abstract
1 , U.S. Army Research Lab, Adelphi, Maryland, United States, 2 , U.S. Naval Academy, Annapolis, Maryland, United States, 3 , University of Connecticut, Storrs, Connecticut, United States
Conversion from heat into electricity provides a majority of electrical power today and is expected to remain so given the high energy density of hydrocarbon fuel combustion. Pyroelectrics can convert energy by cycling around thermally- and electrically-induced polarization changes, where the energy density scales with the product of the polarization change and applied field . To maximize the work per cycle and thus the efficiency, one would want to operate in the vicinity of a temperature-induced phase transition and under the largest applied field allowable. Following this logic, an extremely large energy conversion potential was measured in thin-film lead zirconate titanate (PZT) . The challenges of understanding and operating in this regime are the same as the benefits, the non-linearity of the properties of interest, particularly the pyroelectric coefficient, p, and specific heat, Ce, with temperature and electric field.
A non-dimensional coefficient representing the ratio of electrocaloric to specific heat has been created to evaluate energy conversion cycle efficiency. Landau-Ginzburg-Devonshire free energy calculations of varios pyroelectric thin films provide the property relationships with temperature and electric field. The competing maxima of p (representing energy out) and Ce (representing energy in) reveal a non-intuitive peak efficiency operating temperature relative to the zero field phase transition temperature (Tc). At high electric fields where energy conversion is most attractive, p and Ce have been dramatically diminished and there is a second peak of efficiency dominated by the applied field at temperatures 1.2*Tc. This is analogous to operating a steam turbine cycle above the vapor dome where there is no condensation. This work expands upon previous theoretical analysis  to include the necessary electric field and temperature dependencies. We reveal important characteristics of pyroelectric energy conversion cycles in the non-linear, high electric field regime, which is commonly regarded as ideal for conversion applications.  S. P. Alpay, J. Mantese, S. Trolier-McKinstry, Q. Zhang, R. W. Whatmore, MRS Bulletin 2014, 39, 1099,  A. S. Mischenko, Q. Zhang, J. F. Scott, R. W. Whatmore, N. D. Mathur, Science 2006, 311, 1270.  G. Sebald, S. Pruvost, and D. Guyomar, "Energy harvesting based on Ericsson pyroelectric cycles in a relaxor ferroelectric ceramic," Smart Materials and Structures, vol. 17, p. 015012, 2008.
8:00 PM - ES8.8.05
Bending-Mode Elastocaloric Cooling
Darin Sharar 1 , Joshua Radice 2 , Andrew Smith 2 , Brendan Hanrahan 1 , Nicholas Jankowski 1 , Nathan Lazarus 1 Show Abstract
1 , U.S. Army Research Laboratory, Adelphi, Maryland, United States, 2 , United States Naval Academy, Annapolis, Maryland, United States
Hydrofluorocarbon (HFC) refrigerants conventionally used in vapor-compression systems contribute to the depletion of the ozone layer. To limit climate change, legislation has been proposed in the United States, as well as Canada, Mexico, and the European Union, to phase out HFCs. Strain-induced elastocaloric cooling, using shape memory alloys (SMAs), offers a promising alternative to vapor-compression systems, with theoretical and observed COPs as high as 11. SMAs offer additional advantages in size and noise, as well as environmental benefits from the elimination of HFC refrigerants. Most experiments demonstrating these benefits have characterized SMA performance based on uniaxial tension and compression. Only a few researchers have considered material performance and cooling system architectures for bending-mode elastocaloric cooling despite the benefits of reduced actuation force (due to the smaller activation volume and force multiplication using lever arms) and point-source cooling at the bending location, among others. These benefits come at the expense of reduced activated volume due to low strain near the neutral axis.
Experimental results with 1mm-diameter Nitinol (NiTi) shape memory alloy wires will be presented in order to evaluate the strengths and weaknesses of bending-mode architectures. Tensile testing, performed on an Instron tool (uniaxial) and with custom fixtures (bending), and simultaneous IR thermography allow the effects of strain rate (from .001 to 1 s-1) and strain mode on the temperature evolution, COP, cyclic histories, and shakedown to be determined. Benchmark uniaxial results, show a strain-induced temperature reduction of 16°C, calculated material latent heat of 6.52 J/g, and a material coefficient of performance (COP) of 2.15. These results are on par with results found in the literature. Preliminary bending-mode experiments, performed using the same material set, show a temperature reduction of 6°C but further experimental analysis is needed to determine the magnitude and quality of enhancement/degradation compared to uniaxial operation. Euler-Bernoulli beam theory will be used to correlate expected global mechanical behavior to experimental bending results and compliance/deviation from expected results will be reported.
8:00 PM - ES8.8.06
Magetocaloric Effect in Severe Plastically Deformed Ferromagnetic 4-f Elements—Gd, Tb, Dy, Ho and Er
Sergey Taskaev 1 2 , Konstantin Skokov 1 , Vladimir Khovaylo 2 , Dmitriy Karpenkov 2 , Maxim Ulyanov 1 , Dmitriy Bataev 1 Show Abstract
1 , Chelyabinsk State University, Chelyabinsk Russian Federation, 2 , National University of Science and Technology (MISIS), Moscow Russian Federation
In this work we continue our previous investigations of the severe plastic deformation on the magnetic properties of 4-f elements, with special accent on magnetocaloric effect. As it shown in , severe plastic deformation has a great effect on magnetic properties of 4-f elements. For instance, in Gd a significant increase of the magnetocrystalline anisotropy (up to 2 orders of magnitude) has been observed. The reason of such behavior is in a giant magnetic anisotropy induced by SPD. This unexpected phenomena drives to a new thermodynamic and magnetic properties of severely deformed Gd ribbons  which could be completely restored after heat treatment procedure. The heat treatment regimes are directly connected with the degree of plastic deformation . Qualitatively the same behavior observed for other 4-f elements – terbium and dysprosium .
The interest in this matter is far from being purely academic. High pressure torsion (HPT) is very interesting technique for designing novel functional materials. Depending on the degree of deformation, magnetic, structural or thermodynamic properties could be varied in severely deformed materials.
In the talk we report the influence of high pressure torsion on magnetic, structural and thermodynamic properties of Gd, Tb, Dy, Er and Ho samples treated with the help of HPT technique. High pressure torsion was performed under 6 GPa with 5 complete turns at room temperature. This feature is helpful for designing novel magnetic materials (especially hard magnetic materials).
Authors appreciate Russian Science Foundation grant 15-12-10008 for financing this work.
 S. V. Taskaev, M. D. Kuz`min, K. P. Skokov, D. Yu.Karpenkov, A. P. Pellenen, V. D. Buchelnikov and O. Gutfleisch, JMMM 331, 33 (2013).
 S. V. Taskaev, V. D. Buchelnikov, A. P. Pellenen, M. D. Kuz’min, K. P. Skokov, D. Yu. Karpenkov, D. S. Bataev and O. Gutfleisch, J. Appl. Phys. 113, 17A933 (2013).
 Sergey V. Taskaev, Konstantin Skokov, Vladimir Khovaylo, Dmitriy Karpenkov, Maxim Ulyanov, Dmitriy Bataev, Anatoliy Pellenen. Abstracts of MRS Spring Meeting, MD9.8.04 (2016).