Symposium OrganizersJun-ichi Shimoyama, University of Tokyo
Eric Hellstrom, Florida State University
Marina Putti, University of Genova and CNR-SPIN
Kaname Matsumoto, Kyushu Institute of Technology
Takanobu Kiss, Kyushu University Research Institute of Superconductor Science and Systems
Symposium Support Japan Society of Applied Physics
I3: Microstructure and Related Properties of 2G Conductors
Tuesday PM, April 10, 2012
Moscone West, Level 2, Room 2009
2:30 AM - *I3.1
Nanostructural Characterization of Artificial Pinning Centers in RE-123 Thin Film by Three-dimensional Electron Tomography Using TEM
Kenji Kaneko 1 Takeshi Nishiyama 1 Kazuhiro Yamada 1 Takeharu Kato 2 Teruo Matsushita 3 Yutaka Yamada 4 Teruo Izumi 4 Yu Shiohara 4
1Kyushu University Fukuoka Japan2JFCC Nagoya Japan3Kyushu Institute of Technology Iizuka Japan4ISTEC Tokyo JapanShow Abstract
In the real life, almost all materials are imperfect and contain impurities introduced intentionally to enhance the properties of materials. The controlling of impurities so that the second phases caused by them are of great importance in materials science and engineering. It is therefore that the nanoscale characterizations of these impurities and second phases in three-dimensions (distribution, morphology, volume, etc.) are of worthwhile for improving the property and further design of materials. Among characterization methods to achieve three-dimensional information at nanoscale resolution, three-dimensional electron tomography, by combination of transmission electron microscopy and computed tomography (TEM-CT), has been applied for materials science in recent years. During my talk, three-dimensional nano-characterization of REBCO-123 type high-temperature superconductors (HTSCs) containing artificial pinning centers in various dimensions, will be presented. This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) as the Materials and Power Application of Coated Conductors Project (M-PACC Project).
3:00 AM - *I3.2
Nanostructural Characterization of YxGd1-xBa2Cu3Oy Layers Containing BaZrO3 Particles Fabricated by Metal Organic Deposition
T. Kato 1 Y. Takahashi 2 R. Yoshida 1 M. Yoshizumi 2 T. Izumi 2 T. Hirayama 1 Y. Shiohara 2
1JFCC Nagoya Japan2ISTEC Tokyo JapanShow Abstract
Many research efforts have been attempted to introduce nano-sized non-superconductive particles to act as artificial pinning centers (APCs) in REBa2Cu3Oy superconductive layers on a metallic substrate with a textured buffer layer. These coated conductors with APCs are indispensable to develop industrial applications. One of the promising processes is to control nano-sized BaZrO3 (BZO) particles in YxGd1-xBa2Cu3Oy (YGdBCO) layers by trifluoroacetates-metal organic deposition (TFA-MOD). Recently two-step crystallization process in the TFA-MOD has been found to be very effective to enhance in-field critical currents significantly. However, the effects on the microstructure and the mechanism for the improvement have not yet been understood. In order to optimize the process conditions, we need to understand the structural change in the two-step crystallization process. In this study, we prepared precursor films, for which both MOD solution coating and drying process was repeated using reel-to-reel tape transfer system, quenched films during the two-step crystallization process and a final crystallization film. The nanostructures of these films were investigated sequentially by transmission electron microscopy. Multi-layered structures corresponding to the coating process of the TFA-MOD were found in the precursor film, which was composed of tiny grains. The boundary of each layer in the precursor film had Cu-rich content. During the interim annealing at 848K, the tiny grains grew larger, and BZO particles were gathered around the boundaries of the Cu-rich regions. When these films were heated up at 1038 K, c-axis oriented YGdBCO grains formed on the buffer layer. Numerous BZO particles with an average size of 20 nm formed in the precursor film, and some BZO particles were trapped in the c-axis oriented grains. Finally, a dense YGdBCO layer was formed, which was mainly composed of c-axis oriented grains. In addition, the BZO particles, which had formed in the precursor, were distributed in the YGdBCO layers. Though some of the BZO particles were aligned perpendicularly to the substrate normal, these particles were homogenously distributed in the YGdBCO layer. On the contrary, larger elliptical pores were formed in an YGdBCO layer fabricated by conventional one-step crystallization process, and BZO particles clamped together in the layer. Based on these insights, we can obtain design guidelines to produce high-performance superconductive layer in high magnetic fields. This work was supported by New Energy and Industrial Technology Development Organization (NEDO) as the project for Development of Materials & Power Application of Coated Conductors.
3:30 AM - I3.3
Coordinated Analysis of Current Limiting Obstacles in Sm1Ba2Cu3O7-delta; Coated Conductors by Hybrid Microscopy Techniques
Takanobu Kiss 1 Arkadiy Matsekh 1 Masayoshi Inoue 1 Takato Kaijhara 1 Ken-ichi Ikeda 1 Satoshi Hata 1 Hideharu Nakashima 1 Gracia Kim 2 William Jo 2 Hong-Soo Ha 3 Sang-Soo Oh 3 Seung-Hyun Moon 4
1Kyushu University Fukuoka Japan2Ewha Womans University Seoul Republic of Korea3Korea Electrotechnology Research Institute Changwon Republic of Korea4SuNAM Seoul Republic of KoreaShow Abstract
Using multiple microscopy techniques, we have carried out combined analysis to reveal both the superconducting and micro-structural properties in Sm1Ba2Cu3O7-Î´ (SmBCO) coated conductors (CCs). Al2O3, Y2O3, IBAD-MgO and LaMnO3 layers were deposited sequentially on a Hastelloy substrate to obtain bi-axially textured template. Successively, 2 Î¼m thick SmBCO layers have been deposited by batch type co-evaporation process using drum in dual chambers method. In order to investigate current limiting mechanism, we first carried out laser induced thermoelectric effect (LITE) imaging by laser scanning microscopy at room temperature to visualize in-plane distribution of CuO2 tilting domains and defects in SmBCO layers. It is followed by the low temperature laser scanning microscopy (LTLSM) cooling down the sample to superconducting state. We successfully visualized local flux flow dissipation as a function of bias current. From these analysis, we can determine the position of current limiting obstacles with Î¼m resolution. Lastly, micro-sampling transmission electron microscopy (TEM) has been carried out. It allows us to investigate crystallographic structure at the obstacles in nm scale. We found that the amplitude of LITE signal shows very good linearity as a function of CuO2 tilting angle which was determined from the coordinated cross-sectional TEM observation. Since the LITE has a good compatibility with the LTLSM and also has a robustness against surface contamination, it is very effective method to analyze the crystallinity in the SmBCO layers. TEM analysis also clearly shows that current blocking obstacles in the SmBCO layer in the present sample is originated from deformation of the Hastelloy substrate such as grain boundaries and high density dislocations. Namely, the quality of Hastelloy surface is crucial to improve superconducting performance of these CCs. This work was partly supported by JSPS: KAKENHI (20360143).
3:45 AM - I3.4
Estimation of Local Current Transport Properties in Thin Film Superconductor Based on Scanning Hall-probe Microscopy
Kohei Higashikawa 1 Kei Shiohara 1 Masayoshi Inoue 1 Takanobu Kiss 1 Masateru Yoshizumi 2 Teruo Izumi 2
1Kyushu University Fukuoka Japan2International Superconductivity Technology Center Tokyo JapanShow Abstract
To enhance a global critical current in a superconductor, it is indispensable to understand current limiting factors and their influence on such a critical current. From this point of view, we have investigated in-plane distribution of local critical current density and its dependence on electric field criterion in a thin-film superconductor by using scanning-Hall probe microscopy. In a remanent state after the application of sufficiently high magnetic field to a sample, current flows at critical current density according to the critical state model. Such distribution of current density was estimated from that of measured magnetic field by considering Biot-Savart law. Furthermore, the corresponding electric field criterion was evaluated from the relaxation of such remanent magnetic field by considering Faradayâ?Ts law. This means that we could estimate in-plane distribution of local critical current density as a function of electric field criterion in a nondestructive manner. This characterization method would be very helpful for finding current limiting factors in a thin-film superconductor and their influence on its global current density versus electric field properties which would usually be obtained by 4-probe method.
This work was supported by "The New Energy and Industrial Technology Development Organization (NEDO), â?oJSPS: KAKENHI (23760263)â? and â?oThe Nakajima Foundation".
I4: AC Loss of 2G Conductor and Bi-based Materials
Tuesday PM, April 10, 2012
Moscone West, Level 2, Room 2009
4:30 AM - I4.1
A Simple, Cost Effective Method to Achieve Fully Filamentized Low AC Loss 2G HTS Coated Conductors
Ibrahim Kesgin 1 Xinwei Cai 1 Goran Majkic 1 Eduard Galstyan 1 Changhui Lei 2 Venkat Selvamanickam 1
1University of Houston Houston USA2SuperPower Schenectady USAShow Abstract
Manufacturing low AC loss high temperature superconductor (HTS) coated conductors (CCs) required for AC applications, such as fault current limiters, transformers, and generators have always been challenging. Subdividing CCs into filaments has been shown as a viable method to reduce AC losses. In this regard, different techniques have been developed to construct desired filamentized configuration of CCs to obtain minimal AC losses. Complexity, difficulty to control, limited throughput, and high cost are some of the drawbacks regarding with these techniques. We have implemented a simple, cost effective and readily scalable method for making filaments on our REBCO CC made by metal organic chemical vapor deposition (MOCVD). We have also successfully fabricated fully filamentized conductors after electrodeposition of copper stabilizer layer. We have observed that the copper stablizer provides no-contribution to AC losses while significant contribution to AC losses was observed in case of copper in the non-filamentized conductor. AC losses of striated conductors as well as a reference non-striated conductor both before and after electrodeposition were measured in AC magnetic fields normal to the conductor at various frequencies. After 11 striations, at least 11 fold reduction in AC losses, which is very close to the theoretically estimated value, was obtained at AC field of around 40 mT, and 77K. In this presentation, AC loss measurements, physical properties, and microstructure of mechanically multifilamented conductors will be discussed.
4:45 AM - *I4.2
Microstructure and Current Transport in High Jc, Macroscopically Untextured Bi2212 Polycrystals
Fumitake Kametani 1 Jianyi Jiang 1 Eric Hellstrom 1 David Larbalestier 1
1NHMFL, FSU Tallahassee USAShow Abstract
Almost all high Tc superconductors such as YBCO, Bi-2223 or the recently discovered pnictides possess grain boundaries that tend to block current. In the case of planar grain boundaries, an exponential decay of the critical current density Jc with increasing misorientation angle Î¸ is observed. For polycrystalline versions of these materials to have high Jc we must develop a uni- or biaxial textured architecture. However there is one interesting exception to this rule, Bi2212. Macroscopically untextured Bi2212 round wire can achieve a high Jc of ~105 A/cm2 at 4.2 K and 45 T. In order to explore how such a high Jc is possible where many high angle grain boundaries occur in the round wires, we have been combining high resolution SEM imaging, EBSD-OIM, and FIB-extraction to local Jc measurements. Firstly the experiments have been carried out on much denser Bi2212 bulk with high intergrain Jc. By measuring the V-I characteristics of extracted individual filaments, we certainly can see that weak-link-free current paths exist in filaments and we are now focusing on individual grain boundaries of varied misorientation angles. The goal of our experiments is to understand those factors which make Bi2212 grain boundaries special. Our hope is that such information will enable better grain boundary current transfer in other high Tc materials such as YBCO.
5:15 AM - I4.3
Bi-2223 Wire Development for HTS Applications
Hitoshi Kitaguchi 1 Shin-ichi Kobayashi 2 Kazuhiko Hayashi 2
1National Institute for Materials Science Tsukuba Japan2Sumitomo Electric Industries, Ltd. Osaka JapanShow Abstract
Twenty five years have passed since the first discovery of high-Tc superconductors (HTS). Today, HTS applications are truly expected to revolutionize energy technologies such as DC and/or AC power transmission cables, highly efficient and compact motors and generators, etc. The most important development toward realizing innovation using HTS will be to improve the current carrying capacity of HTS wires. (Bi,Pb)2Sr2Ca2Cu3Ox(Bi-2223) tapes are now commercially produced and used in various proto-type applications. DI-BSCCO is the high performance silver-sheathed Bi-2223 wires produced with the controlled-overpressure (CT-OP) sintering technique. The present commercial DI-BSCCO can provide the uniform high critical current up to 180 A (@77K, self-field) over 1km. Continuing efforts have been performed in fundamental HTS materials science as well as wire processing aimed at doubling the current carrying capacity of Bi-2223 wires. Some short length test pieces exhibit 250 A (@77K, self-field) as the highest critical current (corresponding to 600 A per 1 cm-width). The performances of DI-BSCCO can meet the growing needs for various HTS applications. In this presentation, current carrying performance of recent Bi-2223 wires will be reported.
5:30 AM - I4.4
Grain Boundary Engineering by Post Annealing for Cuprate Superconductors
Jun-ichi Shimoyama 1 Akiyasu Yamamoto 1 3 Hiraku Ogino 1 Kohji Kishio 1 Tomohiro Kagiyama 2 Shin-ichi Kobayashi 2
1University of Tokyo Tokyo Japan2Sumitomo Electric Industries, Ltd. Osaka Japan3JST-PRESTO Tokyo JapanShow Abstract
In the most of cuprate superconductors, the post annealing process is well recognized to be quite important for controlling nonstoichiometric oxygen composition, which affects both intragrain and intergrain characteristics. However, very few attentions have been paid for the effects of post annealing on the cation composition of the layered cuprates in spite of its serious influence on the critical current properties of the material. Tc of Bi2223 was found to increase up to ~118 K by post annealing at ~1000 K for a long time accompanying an increase in the c-axis length in our previous study. This result gave a hint to increase critical current of polycrystalline Bi2223 tapes by enhancement of Tc, i.e. an increase in condensation energy, which was suppressed somehow by nonstoichiometric cation composition. In the present study, we have systematically studied the post annealing effect on the grain coupling characteristics of various cuprate superconductors. In the case of the randomly oriented Bi2223 sintered bulk specimen, the intergrain Jc enhanced three times by addition of post annealing process under moderately reduced atmospheres at ~1000 K prior to the low temperature annealing to control the oxygen content. Effects of post annealing on the grain boundary characteristics of high-Tc superconductors, such as Bi2223, RE123 and other compounds, will be shown.
I5: Poster Session: Recent Advances in Superconductors
Tuesday PM, April 10, 2012
Moscone West, Level 1, Exhibit Hall
6:00 AM - I5.1
Structural Analysis of Nanoinclusions/YBa2Cu3O7-x Interface by Molecular Dynamics Simulation
Yamato Fujishima 1 Masahiro Yamane 1 Kaname Matsumoto 1
1Kyushu Institute of Technology Kitakyushu JapanShow Abstract
Formation mechanism of nanorods and nanoparticles in YBa2Cu3O7-x (YBCO) films is still uncertain though a huge enhancement of Jc of the films has been reported by introduction of nano-inclusions such as BaZrO3 and Y2O3. In this study, we report on the new finding concerning the formation mechanism of nanorods and nanoparticles in the YBCO films obtained by using a molecular dynamics (MD) simulation. The MD calculation was executed by assuming the film deposition condition, and using a large-scale nanoparticle/YBCO interface model. The interfacial energy was calculated from the internal energy after MD simulation, and the strain distribution in the YBCO area was estimated from the local structural changes. As a result, it was clarified that the interfacial energy was more predominant than the strain energy in the formation mechanism of nanorods and nanoparticles. We also report the comparative study of nanoinclusions/YBCO interfaces by using transmission electron microscopy (TEM) and X-ray diffraction.
6:00 AM - I5.11
Preparation of Superconducting REBa2Cu4O8 (RE=Y, Yb) Thin Films by Using Pulsed Laser Deposition and Chemical Solution Deposition
Shingo Fukushima 1 Kaname Matsumoto 1 Yutaka Yoshida 2 Satoshi Awaji 3 Yoshihiko Takano 4
1Kyushu Institute of Technology Kitakyushu Japan2Nagoya University Nagoya Japan3Tohoku University Sendai Japan4NIMS Tsukuba JapanShow Abstract
The crystal structure of YBa2Cu4O8 resembles that of YBa2Cu3O7-x, the difference being a doubling of the so called chains with respect to YBa2Cu3O7-x, causing the c axis to more than double. Due to this double chain all the oxygen atoms have a strong bond with a copper atom, resulting in fixed and stable oxygen content, so that YBa2Cu4O8 is essentially oxygen-stoichiometric and is expected as a thermally stable compound. However, it is practically difficult to produce the YBa2Cu4O8 phase because of its limited stability region in the phase diagram of the Y-Ba-Cu-O system. YBa2Cu4O8 phase is thermodynamically stable at low temperatures and higher oxygen pressures than YBa2Cu3O7-x. Since controlling of higher oxygen pressures is difficult for growing films by physical vapor deposition processes, post annealing is necessary. We report the preparation of REBa2Cu4O8 (RE=Y, Yb) thin films by using pulsed laser deposition and chemical solution deposition processes. YBa2Cu4O8 precursor films deposited on single crystal substrates by pulsed laser deposition were solid-state reacted in the post annealing processes. The epitaxially grown films showed the superconductivity, but the c-axis of the films was in-plane oriented. YbBa2Cu4O8 films were prepared on single crystal substrates by chemical solution process. The films heat treated at ambient oxygen pressure showed metallic behavior and sharp superconducting transition. These films were stable under the high temperatures and low oxygen pressures. The growth mechanism of the films will be discussed.
6:00 AM - I5.12
Electronic Structure of Some Ternary Cuprates and High-Tc Superconductors
Peter Karpovich Nikolyuk 1 Svitlana Lukijanchuk 1 Tatijana Grushchenko 1 Vladislav Stasenko 2
1Vinnitsa Co-operative Institute Vinnitsa Ukraine2Vinnitsa National Technical University Vinnitsa UkraineShow Abstract
During the last years in scientific literature row of reports about atomic-scale perturbation charges in high temperature superconductors (HTSC) have appeared. The question is about the so-called stripes and checkerboard patterns which appear as a result of electronic states modulation. The occurrence of such anomalies in the division of the electronic states causes the special interest because can be related to creation of NTSCâ?Ts high-temperature superconductivity state. The charge increasing means strong correlations of the spins and charge states of HTSC. Thus, there is a question to these modulations origin nature and their influence on high- temperature superconductivity state. With the purpose of physical nature investigation of the highpointed anomalies X-ray and photoemission studies of some ternary compounds of the R-Cu-Si system (R-rare-earth metal) and high-temperature superconductor had been performed. Such objects selection is caused fact that all named compounds are cuprates, in which the dehibridization phenomenon had been found. The dehibridization of electronic states especially evidently shows up in X-ray emissions spectra, consideration of which peculiar attention are spared in this investigation. It is important to note that in the case of HTSC the role of dehibridization factor is carried out hybrid orbitals - type, which form plattigu. Oxygen, which is a strong oxidizer, destroys 3d-shell and forms power strong pointed up orbitals. Thus, power stableness of Cu3d10 shells caused that of - hybrid orbitals. Exactly the Cu-O planes are basic objects (in the sense of transition to superconducting state) in the structure of HTSC, which are accountable for superconducting state origin. On our mind the dehibridization process causes occurrence stepped off electronic states. The quantum interference such states can result in stripes and checkerboard patterns.
6:00 AM - I5.13
Insulator-superconductor Transition in Nano-composites: Built from bi-Layers of Co Clusters and Bi
Wiliam Trujillo Herrera 1 Isabel Dinoacute;la 1 Chachi Rojas-Ayala 1 Yutao T Xing 2 Hans Micklitz 1 Elisa Baggio-Saitovitch 1
1Centro Brasileiro de Pesquisas Fiacute;sicas Rio de Janeiro Brazil2Universidade Federal Fluminense Niteroacute;i BrazilShow Abstract
Superconductivity (SC), ferromagnetism (FM) and topological Insulators (TI) are the ingredients in the actual field of research in novel compounds in nanometer scale. SC-FM nano-composites can be fabricated, for example, by depositing in-beam prepared well-defined FM clusters of nanometer size and trapping them in SC matrix by depositing them onto a cold substrate. This technique was successfully employed in the past with SC Pb wherein FM Co particles have been embedded [1,2]. In these experiments the formation of spontaneous vortices without the application of an external magnetic field or any macroscopic magnetization has been observed. In the present work we show some evidence for the competition between Mott insulator (IS) like behavior and SC in as prepared samples and competition between SC and TI in annealed samples Co-clusters/Bi bi-layers. We deposited an amorphous Bi film at 4.2 K with a thickness between 3 and 7 nm on top of former deposited Co clusters having a mean size of â?^ 4.5 nm. Total amount of deposited clusters corresponds to a mean layer thickness between 0.7 and 5.5 nm. In-situ transport measurements were performed between 2 and 100 K. Electrical resistance measurements on as prepared samples show hopping (tunneling) conductivity as Ïf = Ïf0 exp[-(T0/T)1/2] above the superconductor transition (Tc) and the re-entrance into the normal state with hopping (tunneling) conductivity again below Tc. After heating up to â?^ 60 K the amorphous Bi crystallized. Pure crystallized Bi films show the typical behavior of a two-dimensional metal with weak localization due to some disorder and no indication of superconductivity. The crystallized Bi films on top of the Co-clusters, on the other hand, show a strong increase in resistivity Ï with decreasing temperature and the sharp drop in Ï at Tc. This can be explained by an opening of a gap in the density of states (DOS) at the Co/Bi interface layer of the Bi film due to the presence of Co magnetic moments. Such an opening of gap in the DOS has been predicted at the surface of traditional TI like Bi3Se2, decorated with magnetic impurities [3,4].  Y. T. Xing et al. Phys. Rev. B 78, 224524 (2008).  Y. T. Xing et al. Phys. Rev. B 80, 224505 (2009).  Hai-Zhou Lu et al. Phys. Rev. Lett. 107, 076801 (2011).  Hai-Zhou Lu et al. Phys. Rev. B 84, 125138 (2011).
6:00 AM - I5.15
Pressure-composition Phase Diagrams of Doped BaFe2As2 Single Crystal Grown from In-flux
Cris Adriano 1 Thales Garitezi 1 Priscila F Rosa 1 Pascoal Joseacute; Giglio Pagliuso 1
1Universidade Estadual de Campinas Campinas BrazilShow Abstract
We report the evolution of the pressure-temperature phase diagrams of the Ba(Fe1-xMx) 2As2 (M = Co, Cu, Ru, Mn) single crystals grown from In-flux. We compare the effects of the applied pressure in samples with different concentrations of M but with the same temperature for the onset of the spin density wave (TSDW) at ambient pressure by following the evolution of the magnetic and uperconducting (SC) phases as a function of the pressure. The electrical resistivity measurements under pressure for samples that belong to the under-doped region of the phase diagram showed that TSDW decreased and the SC phase is achieved at high pressures with Tc) creaching a maximum value of 28 K for P â?^ 16 kbar for x = 0.03 of M = Co doping. We also discuss how the critical pressure for inducing SC depends on the particular M-doping with and also the influence of the growth route by comparing our pressure-temperature phase diagram with one constucted form the samples grown using the self-flux method.
6:00 AM - I5.16
Chemical Compositions and Physical Properties of (Fe2As2)(Ca-(M,Ti)-O) System
Kenji Machida 1 2 Hiraku Ogino 1 2 Akiyasu Yamamoto 1 2 Kohji Kishio 1 2 Jun-ichi Shimoyama 1 2
1The University of Tokyo Tokyo Japan2JST-TRiP Tokyo JapanShow Abstract
Recently iron-based superconductors have attracted attention as new high-Tc superconductors. They have alternate stacking structure of iron-pnictide layers and blocking layers. In particular, we have focused on iron pnictides with perovskite-type blocking layer, because they have chemical and structural flexibilities. Recently, we found iron arsenide superconductors with very thick perovskite-type blocking layers such as (Fe2As2)(Can+1
(Sc,Ti)nOy) (n = 3,4,5), (Fe2As2)(Can+1
(Mg,Ti)nOy) (n = 3,4) and (Fe2As2)(Can+2
(Al,Ti)nOy) (n = 2,3,4). They exhibit superconductivity at higher than 40 K without intensive carrier doping. Up to now, their carrier-doping state is not clear while cation/anion nonstoichiometry such as oxygen deficiency or M/Ti ratio is expected. Control of these nonstoichiometry and investigation of their effects on physical propereties have been attempted in the present study. All samples were synthesized by the solid-state-reactions. Starting reagents were mixed and pelletized in a glove box filled with argon gas. These pellets were sealed in evacuated quartz ampoules and heated at 1100Â°C for 72 h. Constituent phases and the lattice constants were determined by powder X-ray diffraction. Temperature dependence of magnetization was measured by a SQUID magnetometer. Electric resistivity was measured by the AC four-point-probe method. There was no significant difference in lattice constants of (Fe2As2)(Ca5(Sc,Ti)4Oy) with different Sc/Ti ratio in starting compositions. This indicated that nonstoichiometry in Sc/Ti ratio of this material is not large. On the other hand, lattice constants of (Fe2As2)(Ca6(Al,Ti)4Oy) were changed by different starting Al/Ti ratios. Their Tc were also changed with Al/Ti ratio and it seemed that there is correlation between Tc and c-axis length. On the other hand, temperature dependence of resistivity of (Fe2As2)(Ca6(Al,Ti)4Oy) with different Al/Ti ratio indicated similar behavior with each other in normal state, suggesting that there is no significant change in carrier-doping state with Al/Ti ratio. This suggested that local structure of Fe2As2 layer such as As-Fe-As bond angle or pnictogen height are determining factors of Tc for these compounds. Effect of oxygen annealing on (Fe2As2)(Ca5(Sc,Ti)4Oy) and (Fe2As2)(Ca6(Al,Ti)4Oy) will be also reported.  H. Ogino et al., Supercond. Sci. Technol.24 (2011) 085020.
6:00 AM - I5.17
Synthesis and Physical Properties of New Iron Phosphide (Fe2P2)(Sr3Sc2O5)
Yasuaki Shimizu 1 2 Hiraku Ogino 1 2 Akiyasu Yamamoto 1 2 Kohji Kishio 1 2 Jun-ichi Shimoyama 1 2
1The University of Tokyo Tokyo Japan2JST-TRiP Tokyo JapanShow Abstract
Since high Tc superconductivity in LaFeAs(O,F) was discovered in 2008, many new superconductors which contain anti-fluorite type Fe2Pn2 layer have been reported. However, further increase in Tc with less toxic elements is required for practical applications. Therefore, it is necessary to explore new iron-based superconductors. Among the iron-based superconductors, a series of compounds containing perovskite-type blocking layer have high chemical and structural flexibility at the perovskite-type layer. In this system, a lot of iron arsenides, such as (Fe2As2)(Can+1(Sc,Ti)nOy) with large variety of crystal structures and compositions are reported. On the other hand, only three iron phospides, (Fe2P2)(Sr4Sc2O6) (Tc ~17 K), (Fe2P2)(Ca4Al2O6) (Tc ~17.1 K) and (Fe2P2)(Ca3Al2O5-y) (Tc ~16.6 K) are found in this system so far. Based on these backgrounds, we have explored new layered iron phosphides in this system and discovered (Fe2P2)(Sr3Sc2O5). Samples were synthesized by solid-state reaction under ambient pressure or high pressure synthesis starting from FeP, FeAs, Sr, SrO and Sc2O3 powders. Since some of starting materials are sensitive to moisture or oxygen in air, powders were mixed and pelletized under an inert gas atmosphere in a glove box. Samples were reacted at 1200 ~ 1250Â°C for 120 h in evacuated quartz ampoules or at 1600 Â°C for 2 h under 3.5 ~ 4.5 GPa. Phase identification and evaluation of lattice constants were carried out by X-ray diffraction (XRD) using silicon powder as the internal standard. Magnetic susceptibility was measured by a SQUID magnetometer and electric resistivity was studied by the AC four-point-probe method. (Fe2P2)(Sr3Sc2O5) was formed as a main phase with impurity phases under only high pressure. Lattice constants of the compound were a = 4.038 Ã. and c = 26.37 Ã.. The a-axis length of the compound is longer than that of (Fe2P2)(Sr4Sc2O6) (a = 4.016 Ã.) and the longest among the layered iron phosphides. On the other hand, superconducting transition was not observed above 2 K, indicating that superconducting properties of iron phosphides change greatly by a small difference in the local crystal structures. In addition, substitution of As for P site of (Fe2P2)(Sr3Sc2O5) was attempted. (Fe2(P1-xAsx)2)(Sr3Sc2O5) (x = 0.1 ~ 0.5) were formed under ambient pressure while (Fe2P2)(Sr3Sc2O5) was only formed under high pressure. Their a and c-axis length increased with increasing As ratio. The samples for x = 0.1 ~ 0.33 exhibited superconductivity and the highest Tc was 15 K for x = 0.2 in magnetization.  Y. Kamihara et al., J. Am. Chem. Soc. 130 (2008) 3296.  H. Ogino et al, Supercond. Sci. Technol. 22 (2009) 075008.  P. M. Shirage et al, J. Am. Chem. Soc. 133 (2011) 9630.
6:00 AM - I5.18
Improvement of Superconducting Properties of Ca-RE-Fe-As
Hiroyuki Yakita 1 2 Hiraku Ogino 1 2 Yujiro Hayashi 1 2 Akiyasu Yamamoto 1 2 Kohji Kishio 1 2 Jun-ichi Shimoyama 1 2
1The University of Tokyo Tokyo Japan2JST-TRIP Tokyo JapanShow Abstract
Since the discovery of new superconductor LaFeAs(O,F) (Tc = 26 K) in 2008, Fe-based pnictides or chalcogenides have attracted great attention as new high-temperature superconducting materials. Fe-based superconductors are promising materials because of their high Tc (~55 K) and very high upper critical field. AEFe2As2 (122) superconductors are particularly examined for applications, such as wire, rods and thin films, due to their simple crystal structure, small anisotropy and relatively high Tc, which is achieved by partial substitution of K for the AE site. Recently, it was reported that CaFe2As2 show superconducting transition at approximately 40 K by partial substitution of RE (RE = La, Ce, Pr, Nd) for Ca. However, superconductivity is reported only for single crystalline samples and their superconducting volume fraction is not large. Based on these backgrounds, we have attempted to improve superconducting properties of the Ca-Pr-Fe-As system. Single crystalline and polycrystalline samples with several starting compositions were synthesized under various heat-treatment conditions in evacuated quartz ampoules. Excess FeAs was added for the single crystal growth. Constituent phases and lattice parameters of the resulting samples were analyzed by the X-ray diffraction (XRD) method. Magnetic susceptibility measurement was performed by a SQUID magnetometer and electric resistivity was measured by the AC four-point-probe method. The single crystalline samples of CaFe2As2 with nominal compositions of Ca
1-xPrxFe4As4 (x = 0.14, 0.20) showed superconducting transition at 35 K though superconducting volume fraction was small. On the other hand, all polycrystalline samples with nominal compositions of Ca0.9Pr0.2Fe2As2 and Ca
1-xPrxFe4As4 (x = 0.14, 0.20) sintered under various conditions did not show any sign of superconductivity. A polycrystalline sample with a nominal composition of Ca0.8Pr0.2Fe1.3As1.8 sintered at 1200Â°C for 48 h showed superconducting transition at approximately 20 K and its superconducting volume fraction estimated from ZFC magnetization was large enough to suggest bulk superconductivity. This sample consists of 122 phase, FeAs, PrAs and some unidentified phases. Identifications of the superconducting phase and its chemical composition and optimization of synthesis procedures are ongoing.  Y. Kamihara et al., J. Am. Chem. Soc. 130 (2008) 3296  S. R. Saha et al., arXiv Cond-mat 1105.4798v1
6:00 AM - I5.19
Thin Film Growth of BaFe2(As,P)2 by Molecular Beam Epitaxy
Takahiko Kawaguchi 1 Akihiro Sakagami 1 Toshiya Ohno 1 Masao Tabuchi 2 Toru Ujuhara 3 Yoshikazu Takeda 1 Hiroshi Ikuta 1
1Nagoya University Nagoya Japan2Nagoya University Nagoya Japan3Nagoya University Nagoya JapanShow Abstract
BaFe2As2 turns into a superconductor by doping either Co, K, or P. Many studies on thin film preparation have already been reported for Ba(Fe,Co)2As2 and (Ba,K)Fe2As2 by several groups. However, there had been no report on thin film preparation of BaFe2(As,P)2, although it has a high Tc up to 31 K, which is higher than Ba(Fe,Co)2As2. In this work, therefore, we studied the thin film growth of BaFe2(As,P)2. BaFe2(As,P)2 thin films were grown on LaAlO3 (LAO) or (La,Sr)(Al,Ta)O3 (LSAT) substrates by molecular beam epitaxy. All elements were supplied from solid sources charged in Knudsen cells; Ba, Fe, As, and GaP. The obtained thin films were characterized by x-ray diffraction (XRD), electron probe micro-analysis (EPMA), atomic force microscope (AFM), resistivity, and magnetic susceptibility. First, a non-doped BaFe2As2 thin film was grown on a LAO substrate. The thin film was single phase and c-axis oriented, and the temperature dependence of the resistivity showed an anomaly at about 140 K, as expected for a non-doped sample. Phosphorus flux was then supplied without changing any other growth parameters, and BaFe2(As,P)2 thin films were obtained. Only (00l) peaks of the BaFe2(As,P)2 phase were observed in the XRD patterns of these thin films, indicating that they were single phase and c-axis oriented. The lattice parameter c of the thin films decreased with increasing the vapor pressure of P, indicating that P was successfully substituted for As. Thin films were also grown with various vapor pressures of As, but the P content was almost independent to the vapor pressure of As and depended mostly on the vapor pressure of P. The transition temperature (Tc) varied according to the P content similar to bulk samples. The optimal thin film showed an onset Tc at 30 K with a sharp transition width of 1.5 K, and a smooth surface with a RMS roughness of 1.06 nm.
6:00 AM - I5.2
Relationship between Critical Current Properties and Nanorod Morphology in REBCO Thin Films
Masakazu Haruta 1 Natsuto Fujita 1 Yuta Ogura 1 Takahiro Nakata 1 Toshihiko Maeda 1 Shigeru Horii 1
1Kochi University of Technology Kami-shi JapanShow Abstract
Introduction of nanorods into REBa2Cu3Oy (REBCO, RE denotes rare earth element) thin films is very effective to improve critical current density (Jc) in magnetic fields applied parallel to the c-axis. We have reported that critical current properties in ErBCO thin films with BaNb2O6 (BNO) inclusions prepared by pulsed laser deposition (PLD) [1, 2] were strongly affected by the deposition temperature (Ts), which is due to the change in morphology of nanorods by Ts. In this study, we focused on the Ts dependence of critical current properties in REBCO matrix with two different RE ions. BNO-doped YBCO and ErBCO thin films were grown at various substrate temperatures on SrTiO3 single crystal substrates by PLD using 4th harmonic Nd:YAG-laser. The vortex-Bose-glass-like behavior of irreversibility lines (ILs) emerged for the both BNO-doped YBCO and ErBCO films. The crossover filed (Bcr), which is defined as the border magnetic field between positive curvature and linear portions on ILs, increased with increasing Ts for BNO-doped YBCO. However, in the case of BNO-doped ErBCO, Bcr decreased with increasing Ts. Ts dependences of Jc-B characteristics were also quite different between YBCO and ErBCO system. We will discuss origin of the different Ts dependence of critical current properties from microstructures of nanorods and current-voltage characteristics. This work partially supported by Grants-in-Aid for Scientific Research (No. 23760020) from the Ministry of Education, Culture, Sports, Science and Technology of Japan, and the Research Foundation for the Electrotechnology of Chubu.  S. Horii et al., APL 93 (2008) 152506.,  M. Haruta et al., Physica C 471 (2011) 944
6:00 AM - I5.20
Improvement of the Thin Film Quality of NdFeAs(O,F) Grown by Molecular Beam Epitaxy
Takahiko Kawaguchi 1 Hiroki Uemura 1 Toshiya Ohno 1 Masao Tabuchi 2 Toru Ujihara 3 Yoshikazu Takeda 1 Hiroshi Ikuta 1
1Nagoya University Nagoya Japan2Nagoya University Nagoya Japan3Nagoya University Nagoya JapanShow Abstract
High quality thin films are essential for many applications of superconductors. In our previous studies, we have succeeded in in-situ growth of superconducting NdFeAs(O,F) thin films by molecular beam epitaxy, which showed clear superconducting transitions at high critical temperatures. Here, we report on our study of further improving the thin film quality. We addressed two issues, both important particularly for junction fabrication. First, the surface roughness was significantly reduced because a very thin barrier layer has to be formed on it to fabricate a junction. Secondly, a new method for fluorine doping was developed, because a non-superconducting NdOF cap layer was necessary to form on the NdFeAs(O,F) phase in our previous studies, which was, however, an obstacle for junction fabrication. All the thin films were grown by molecular beam epitaxy. Fe, As, Ga, NdF3 and Fe2O3 charged in Knudsen cells were used as source materials. Here, Fe2O3 was used as an oxygen source. Some of the thin films were grown using O2 gas instead of Fe2O3. First, we investigated the correlation between the growth parameters and the surface roughness of the thin films grown on GaAs substrates. We found that the surface roughness depended strongly on oxygen flux. RMS roughness of a typical non-doped NdFeAsO thin film could be as high as 6.4 nm, which is obviously too large for junction fabrication. By carefully adjusting the oxygen flux, however, the RMS roughness reduced significantly. The optimal condition was very narrow, but a smooth surface with a RMS roughness of about 1 nm was successfully obtained. Thin films with a similarly small RMS roughness were also obtained for MgO and CaF2 substrates. We also developed a new method for fluorine doping in this study, namely in-situ fluorine annealing. A solid source, FeF3, was used to supply fluorine because we found that FeF3 supplies fluorine by thermal decomposition. After growing a non-doped NdFeAsO thin film on a MgO substrate, the thin film was exposed in-situ to fluorine flux at 700Â°C for 30 min. XRD analysis confirmed that the thin film remained a single phase after fluorine annealing. Both a- and c-axis lengths of the thin film decreased with fluorine annealing, and the resistivity showed a clear superconducting transition at about 40 K. The susceptibility measurement confirmed that fluorine was doped to the whole thin film because the volume fraction was almost 100%. In addition, the surface roughness of the F-annealed thin film was still sufficiently small for junction fabrication. We also prepared several thin films and confirmed that doping can be controlled by the annealing condition. These results indicate that a single phase, superconducting thin film can be obtained by in-situ fluorine annealing.
6:00 AM - I5.21
Enhanced Critical Current Properties of Solid-state Reacted MgB2 Wires Using Mechanically Milled and Carbon Treated Boron Powder
Byung-Hyuk Jun 1 Soon-Dong Park 1 Chan-Joong Kim 1
1Korea Atomic Energy Research Institute (KAERI) Daejeon Republic of KoreaShow Abstract
To obtain the MgB2 with high critical current properties, the pre-treatment process of boron (B) powder such as mechanical milling and glycerin carbon (C) doping, and low temperature solid-state reaction of 550 or 600oC were attempted to in situ powder-in-tube processed MgB2/Fe wires. The mechanical milling and liquid glycerin treatment of the B powder were to reduce the grain size of the MgB2 and to achieve homogeneous C incorporation into the MgB2, respectively. The MgB2 phase formation, the full width at half maximum, the critical temperature (Tc), the field dependence of critical current density (Jc) and the temperature dependence of upper critical field (Hc2) were evaluated for MgB2 wires using pre-treated B powders. It was found that the MgB2 phase formation in the wires using the 2 h milled B powder was more activated when compared to the wires using the un-milled B powder under the same heat-treatment conditions, because of the improved reactivity of the B powder after milling. The Hc2 and Jc of MgB2 wire using the milled B powder were enhanced due to a smaller grain size and an increased volume of the superconducting phase. In addition, the low temperature heat-treatment also contributed to the enhanced superconducting properties by minimizing the grain growth for an increased grain boundary pinning when compared to a conventional high temperature heat-treatment of 800oC. The MgB2 wires heat-treated at 600oC for 40 h using ball-milled and glycerin-treated B powder showed the highest transport Jc values at 4.2 K over the entire applied field regime. It was revealed that the grain boundary density was higher and the C substitution also occurred by a low temperature heat-treatment process, which led to a higher Jc. A solid-solid diffusion reaction with the pre-treated B powder resulted in a poor crystallinity with small grain size and an increased lattice disorder, which enhanced the Hc2 and Jc. Acknowledgments; This work was supported by the Power Generation & Electricity Delivery of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by Korea government Ministry of Knowledge Economy. Part of this work was also supported by the National R&D Program of the Ministry of Education, Science and Technology (MEST), Republic of Korea.
6:00 AM - I5.22
Jc-B-T Superconducting Properties of MgB2 Tapes Fabricated by In-situ PIT Method
Akiyoshi Matsumoto 1 Hitoshi Kitaguchi 1 Hiroaki Kumakura 1
1National Institute for Materials Science Tsukuba JapanShow Abstract
MgB2 superconductor is one of candidate for practical use such as MRI magnets and cable at 10 â?" 20 K of liquid hydrogen temperature. The improvement of critical current density (Jc) is important for practical use. In the present study, the temperature dependence and the anisotropy of Jc of powder In tube (PIT) tapes have been investigated. The MgB2 tapes were fabricated by conventional PIT method. We fabricated two kinds of tapes with pure MgB2 and carbon doped tapes using the mixed powders of MgH2 (99.8%), amorphous B(99.99%), nano size SiC(30nm) and the ethyl toluene. These powders were packed in the Fe tube of 6.3mmÏ? in outside diameter and 3.5mmÏ? in the inside diameter, and rolled using grove rolling and flat rolling. Each tapes heat treated at 630oC for one hour in the Ar gas flowing. The XRD peak strength ratio of I002/I110 in the MgB2 powder was about 0.7. On the other hand, the peak ratio of I002/I110 of tapes was almost 2.0 that the value was much higher than those of powder. It was suggested that MgB2 in-situ tapes had an oriented texture in comparison with powder. From the results of the temperature magnetic field dependency of Jc in the pure and C-doped tapes, we found Jc strongly depended on the direction of the magnetic field in a low temperature and high magnetic field. We didnâ?Tt find the big difference between pure and C-doped tapes. We will also discuss about angular and temperature dependence of MgB2 tapes.
6:00 AM - I5.23
Preparation of High Jc MgB2 Films on Aluminum Tapes
Toshiya Doi 1 Hitoshi Kitaguchi 2 Takanori Fujiyoshi 3 Satoshi Hata 4 Yu-ki Kubota 4 Yusuke Shimada 4 Ken-ichi Ikeda 4 Hideharu Nakashima 4 Masao Miyake 1 Tetsuji Hitato 1
1Kyoto University Kyoto Japan2National Institute for Material Science Tsukuba Japan3Kumamoto University Kumamoto Japan4Kyushu University Fukuoka JapanShow Abstract
PIT and the related processes have been developed intensively for fabricating MgB2 superconducting wires, because of their simplicity and potentially low manufacturing cost. However, since the PIT process is based on powder sintering, it is difficult to attain clean grain boundaries or biaxial crystal alignment, which is crucial for achieving high transport critical current density, Jc. Though recent Jc of PIT MgB2 wires well above 10,000 A/cm2 at 4.2 K and 10 T have been reported, the Jc values are still lower than those of the commercial metallic superconductors Nb-Ti and Nb3Sn. The PIT process needs to be improved or a different process needs to be developed for MgB2 to be used in practical applications. In this paper, we will propose a potential alternative. The MgB2 layer without biaxial crystal orientation deposited by an electron beam evaporation technique on an Al tape revealed excellent Jc of about 10 MA/cm2 at 10 K in self field. In contrast to YBCO, as neither biaxial orientation nor high deposition temperature are required for synthesis of the MgB2 layer, it is easy to thicken and to deposit the MgB2 layer on a round shape Al wire, and to enhance the deposition rate. We may expect fairly low production cost of the MgB2 coated conductor.
6:00 AM - I5.24
Josephson Effect Observed in Thin Film of the BSCCO System Heat Treated by Microwave Oven
Claudio L Carvalho 1 Gustavo Q de Freitas 1 Rafael Zadorosny 1 Guilherme B Torsoni 1 Joatilde;o B Silveira 1
1Universidade Estadual Paulista Ilha Solteira BrazilShow Abstract
A centennial after the discovery of superconductivity by H.K. Onnes, more than never before, we can observe how much important it is in our lives (that its higher importance.). Images from the inner human body can be obtained with high resolution predicting as soon as possible diagnosis for some diseases, electrical energy can be transported for long distance almost or without any lost, people can be transported using trains that levitate is almost a reality. All of these examples are becoming a reality due a lot of researches developed looking for new superconductor materials. Then, in this work we have developed a study about how to obtain superconductor thin films of the Bi-system using microwave oven instead electrical furnace or conventional furnace in the thermal treatments. Although, thin films have been prepared in the way to obtain a certain kind of device such as Josephson junctions. Bridge junctions were prepared using optical microscopy and special tools developed in our labs. Electric and magnetic characterization were carried out using dc four probe and PPMS/VSM equipment at 4K-100 K indicating at least two superconducting transitions around 80 K and 100 K, associated to 2212 and 2223 phases, respectively. Structural measurements were also made using, X-ray diffractometry and scanning electron microscopy.
6:00 AM - I5.25
Superconductor Wires Made by PIT Using Powder Obtained from Chemical Process
Claudio L Carvalho 1 Elton J de Souza 1 Gisele A de Souza 1 Gustavo Q de Freitas 1 Rafael Zadorosny 1 Guilherme B Torsoni 1 Hermes A Aquino 1
1Universidade Estadual Paulista Ilha Solteira BrazilShow Abstract
Superconductivity research involving applications have grew a lot in last few years, particularly in the transport of energy, had a promising advance over the years. This study aims to manufacture superconducting wires using the method Powder-In-Tube (PIT). Preliminary studies were done on pellets made of BSCCO powder obtained by polymeric precursors method, and after some results were prepared the superconducting wires. Characterization measurements were made among them the X-ray diffraction, electrical measurements by the method of dc four probes and type of microscopy (FEG-SEM) equipped with EDX to determine the morphology and chemical composition of the sample. X-ray diffraction results showed the formation of the desired phases of the BSCCO system such as Bi-2212, Bi-2223 and Bi-2234 phases. The electrical measurements have detected a sudden drop in electrical resistance of the wires showing the range of superconducting transition with good accuracy. It was possible to perform the calculation of current density in the wires made based on a criterion of 1 Î¼V/cm were obtained and values of around 1,30 â?" 3,90 KA/m2. The values are consistent with the specifications of the samples and within the limits of our research.
6:00 AM - I5.26
High Tc and Jc of Bi,Pb-2223 Thin Film Fabricated by Sputtering Method
Akiyoshi Matsumoto 1 Hitoshi Kitaguchi 1 Toshiya Doi 2 Satoshi Hata 3
1National Institute for Materials Science Tsukuba Japan2Kyoto University Kyoto Japan3Kyushu University Kasuga JapanShow Abstract
Bi2223 thin films on SrTiO3(100) fabricated by DC and RF sputtering have been investigated. According to results of the resistivity-temperature curvatures of as-grown film, the Tc was 72 K, and the temperature transition, Î"T, was also wide. These values were due to the low crystallinity, a kind of deviation in the composition of Bi2223. To obtain the Bi,Pb2223 phase, we annealed the material surrounded with Bi,Pb2223 pellets. On the other hand, Tc = 105 K was obtained in (Bi,Pb)2223 thin film after post-annealing. This Tc value was almost the same value as that of bulk materials of Bi,Pb2223. Furthermore, the transition was also sharper than that of as-grown films. These results suggest that the sputtering deposition and post-annealing process were very effective for obtaining high quality of Bi,Pb2223 thin films. We also checked grain alignments. We observed strong 00l peaks and a sharp quadrupole in X-ray Î¸-2Î¸ and Ï?-scan measurements, suggesting that this film had a single phase of Bi,Pb-2223 and a biaxial orientation. The maximum Jc value of 3.3 x 105 A/cm2 at 77 K was obtained in Bi,Pb-2223 thin film. These Jc values were much higher than that of commercialized Bi,Pb-2223 tapes, suggesting that Bi,Pb-2223 tapes still have the possibility of improvement and enhancement of Jc by controlling the microstructures. Furthermore, from the Jc-B-angle properties, Bi,Pb2223 has very strong anisotropy. This study was partially supported by KAKENHI (22246079) with a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology.
6:00 AM - I5.27
XRD Characterization of Topological Insulator Bi2Se0.3Te2.7
Qiguang Yang 1 2 Doyle Temple 1 Uwe Hommerich 2 EiEi Brown 2 Sudhir Trivedi 3
1Norfolk State University Norfolk USA2Hampton University Hampton USA3Brimrose Corporation of America Baltimore USAShow Abstract
Bi2SexTe3-x system is known for years because of its excellent thermoelectric properties. Recently, its application as a topological insulator has been theoretically predicted and experimentally demonstrated. The bulk of topological insulator is insulating with an energy gap while the surface is metallic with a Dirac cone. This unique property has attracted great attention for investigation of novel quantum phenomena in the field of fundamental physics as well as for potential application in quantum computing. The compound Bi2Se0.3Te2.7 was synthesized in a pre-cleaned quartz ampoule using commercial starting materials of Bi, Te, and Se (5N purity). Further purification of the material was achieved through multiple translations in a horizontal zone-refinement system. The final crystal growth was carried out using Bridgman technique. X-ray diffraction (XRD) techniques were used to characterize the structure of the Bi2Se0.3Te2.7 crystal. The cell parameters as well as the composition of the ternary were measured from the Bragg-Brentano geometry x-ray diffraction measurements. The crystal structure was identified by both Phi-Scan and pole figure measurement. Rocking curve and reciprocal space mapping were also used to get the details of interested crystal planes. The results will be presented and thin film topological insulator using this Bi2Se0.3Te2.7 crystal through pulsed laser deposition will be discussed. Acknowledgment: The work at Hampton University was supported by the National Science Foundation (HRD-0630372 and HRD-1137747).
6:00 AM - I5.3
Flux Pinning Properties and Microstructures of the Multilayered SmBCO Films Doping BSO Nano-rods
Akihiro Tsuruta 1 Yusuke Ichino 1 Yutaka Yoshida 1 Kaname Matsumoto 2 Ataru Ichinose 3 Satoshi Awaji 4
1Nagoya University Nagoya Japan2Kyushu Institute of Technology Kitakyushu Japan3Central Research Institute of Electric Power Industry Yokosuka Japan4Tohoku University Sendai JapanShow Abstract
REBa2Cu3Oy (REBCO) thin films including BaMO3 (BMO, M = Zr, Sn) nano-rods have been reported by many groups. The BMO nano-rods improve the performance of REBCO thin films in magnetic fields. However, they are effective only for magnetic fields applied parallel to the c-axis of the REBCO. In this study, to enhance Jc in the magnetic fields for all applied angles, we fabricated multilayered films consisting of Sm1.04Ba1.96Cu3Oy (SmBCO) and BaSnO3 (BSO) doped SmBCO layers on LaAlO3 (LAO) substrates (multilayered SmBCO film) by PLD method and measured the magnetic field angular dependence of Jc. It was reported that average diameter of BSO was about 10 nm in many studies. Therefore, the thickness of each layer was fixed about 10 nm to form BSO nano-dots. We fixed the number of layers to 32 layers and the total thickness of the film was about 320 nm. We introduced BSO by alternating BSO target and pure SmBCO target in depositing BSO doped SmBCO layers. Typical Tc and Jc of the multilayered SmBCO film were 91.6 K and 3.39 MA/cm2 at 77 K in self-field, respectively. These values were higher than those of a BSO doped SmBCO film without multilayered structure (SmBCO+BSO film) in which BSO was doped by the same method with the multilayered SmBCO film. The typical Tc and Jc of the SmBCO+BSO films were 90.4 K and 2.20 MA/cm2, respectively. In magnetic field angular dependence of Jc (B = 1 T, 77 K), the multilayered SmBCO film had peaks of Jc for B//c and B//ab. The Jc values were 1.15 MA/cm2 (B//c) and 1.53 MA/cm2 (B//ab). The minimum value of Jc was 0.92 MA/cm2. On the other hand, the SmBCO+BSO film had a peak of Jc only for B//c. The Jc value was 1.23 MA/cm2 (B//c) and the minimum value of Jc was 0.51 MA/cm2. Here, we define a as (JcMAX - Jcmin) / JcMAX to express the anisotropy of Jc. The a values (B = 1 T, 77 K) are 0.399 for the multilayered SmBCO film and 0.585 for the SmBCO+BSO film. This result shows that the Jc anisotropy of the multilayered SmBCO film was smaller than the SmBCO+BSO film. In From TEM images, there were BSO nano-dots dispersed at random in the multilayered SmBCO film. It seems that the BSO nano-dots act as 3D-APC at low magnetic field. This work was partly supported by a Grant-in-Aid for Scientific Research (19676005 and 23226014).
6:00 AM - I5.4
Combinatorial Nd:YAG-PLD Method for Investigation of Flux Pinning Materials
Yusuke Ichino 1 Takuya Yoshimura 2 Yutaka Yoshida 2 Ryusuke Kita 3 Kaname Matsumoto 4
1Nagoya University Nagoya Japan2Nagoya University Nagoya Japan3Shizuoka University Hamamatsu Japan4Kyushu Institute of Technology kita-Kyushu JapanShow Abstract
Recently, we have reported that YBCO thin films are grown by PLD method using a forth harmonic Nd:YAG pulsed laser and superconducting properties of the films are comparable to those of films prepared by conventional excimer-PLD method. We concluded that the Nd:YAG-PLD method is promising for coated conductor process. In order to enhance Jc of YBCO thin films under magnetic fields, artificial pinning centers (APC) are doped into the films. For example, BaMO3 (BMO, M=Sn, Zr etc.) is useful as APC due to a formation of nano-rods within the films. However, excess doping of APC reduces the superconducting properties. Therefore, there is an optimal content to maximize the flux pinning performance. Based on above, we used combinatorial Nd:YAG-PLD (C-PLD) method. The C-PLD is an efficient way to screen the optimal APC content, by making it possible to create a film with continuously changing composition across a single substrate. In this study, we investigated a quick screening of the optimal content of APC and an exploration of new APC. At first, we optimized the content of BaSnO3 (BSO) by using the C-PLD method. As a result, we concluded that the optimal content of BSO was around 3.2 vol.%. This value was similar to an optimal value obtained by other groups who prepared their films by using BSO-YBCO mixed targets. From the cross-sectional TEM image of the optimal BSO-doped film fabricated by C-PLD, we confirmed the presence of nanorods made of BSO. Next, in order to explore new APC materials, we doped Ba-based oxides such as Ba3Cu3In4O12 (334) and BaTbO3 (BTO) into YBCO thin films by the C-PLD method. We measured Jc in magnetic fields at various temperatures. At 77 K, the Jc in magnetic fields at 77 K were not so high compared with the BSO doped YBCO films and a pure-YBCO thin film. However, the Jc-B curves were improved with decreasing measurement temperature and became higher than that of the pure-YBCO thin film. This means that the 334 and BTO doped films include small precipitates made of 334 and BTO and the small precipitates would become effective for flux pinning at low temperatures since the coherence length becomes small at low temperature. This work was partly supported by a Grant-in-Aid for Scientific Research (19676005, 20686065 and 23226014).
6:00 AM - I5.5
YBCO/STO Growth on Textured Ni-W Substrates Using Pulsed Electron Deposition
Yasar G. Mutlu 1 Zafer Mutlu 5 Mucahit Yilmaz 3 Oguz Dogan 3 Mihrimah Ozkan 4 Cengiz S. Ozkan 2 5
1Selcuk University Konya Turkey2University of California, Riverside Riverside USA3Selcuk University Konya Turkey4University of California, Riverside Riverside USA5University of California, Riverside Riverside USAShow Abstract
A superconducting YBaCu3O7-Î´ (YBCO) thin film has been produced at 890 oC substrate temperature by pulsed electron deposition (PED) which is an essential and low-cost physical deposition technique of high quality superconducting films. For production of superconducting film, Ni-W textured substrate and SrTiO3 (STO) single buffer layer (instead of multi-layer buffer to reduce the number of processing steps and simplify manufacturing) have been used. The Ni-3%W alloy tapes were used as the metal substrate. The STO targets used in the experiment were prepared by a conventional sintering process. A commercially available YBCO targets was used for deposition of superconducting layer. The texture information was obtained from the XRD analysis. The crystalline structures of Ni-W substrates and YBCO/STO/Ni-W films have been investigated by x-ray diffractometer (XRD). XRD patterns of the substrates consist of (200) and (220) peaks, but with annealing the intensity of (220) peak which means deformation texture decreased, and the intensity of (200) peak which means cube texture increased. It indicates that most of the (200) texture was formed during annealing. The X-ray diffraction analysis suggested that the STO buffer layer and YBCO superconducting layer consisted of randomly oriented polycrystallites. The epitaxial growth of (001)-oriented STO on Ni-W surface was inhibited by the formation of (111) NiO at the oxide/metal interface. The surface morphology and microstructure of YBCO/STO/Ni-W thin film have been characterized with atomic force microscope (AFM) and Scanning Electron Microscope (SEM) .The root-mean-square (Rms) and average (Ra) surface roughness are about 13 nm and 9.6 nm, respectively.
6:00 AM - I5.6
Microstructure Analysis of GdBa2Cu3O7-delta; Coated Conductors by the RCE-DR Process
Soon-Mi Choi 1 Jung-Woo Lee 1 Seung-Hyun Moon 2 Sang-Im Yoo 1
1Seoul National University Seoul Republic of Korea2Superconductor, Nano amp; Advanced Materials Corporation (SuNAM Co.) Ltd Ansung Republic of KoreaShow Abstract
High-Jc GdBa2Cu3O7-Î´ (GdBCO) coated conductors (CCs) was produced by the RCE-DR (Reactive Co-Evaporation Deposition & Reaction) process on LaMnO3-buffered IBAD MgO template. In this study, we have carefully analyzed the microstructural features of GdBCO CCs, including grain boundaries, growth morphologies, interfacial reactions and etc. From these analyses, a large number of inclusions, identified as Gd2O3 second phase particles, were clearly observed in the GdBCO matrix. Even though these particles are potential pinning sites, they are not very effective for the improvement of in-field critical current density (
Jc), which is attributed to rather large sized inclusions. Further details of microstructure analyses of GdBCO CCs by the RCE-DR process will be presented and their effects on the field dependency and anisotropy of
Jc(B,Î¸) values will be discussed.
6:00 AM - I5.8
Relationship between Grain Size and the Degree of Orientation in a Twinned ErBa2Cu3Oy Superconductor Oriented in Modulated Rotating Magnetic Fields
Shigeru Horii 1 Shota Okuhira 1 Momoko Yamaki 1 Masakazu Haruta 1 Jun-ichi Shimoyama 2
1Kochi University of Technology Kami, Kochi Japan2University of Tokyo Tokyo JapanShow Abstract
Recent magnetic orientation techniques enable alignment of three crystallographic axes of substances with structurally low symmetry by usage of a modulated rotating magnetic field (MRF). The technique using MRF is a candidate of production processes of high critical temperature cuprates with orthorhombic structure. Furthermore, another advantageous point in the magneto-scientific process is a room-temperature process without the epitaxial growth. In practice, our group has achieved tri-axial orientation of RE2Ba4Cu7O15-y (RE247, RE=Y) powder in 12T of MRF in epoxy resin at room temperature. Therefore, the magnetic orientation technique is fascinated from the viewpoints of practical production of superconducting bulks and cables. However, in the case of twinned REBa2Cu3Oy (RE123) superconductors, inplane magnetic anisotropy probably disappears in a grain level by the introduction of twin microstructure. In the present study, we focus on a twinned Er123 superconductor, and studied the effects of pulverization time and applied conditions of MRF on the degrees of tri-axial orientation. Consequently, pulverization using ball-milling is found to be a useful process for the achievement of bi-axial orientation of RE123 powders. This work was partly supported by the Asahi Glass Foundation, and the Noguchi Institute.  Fukushima, Horii et al., Appl. Phys. Express 1 (2008) 111701.  Horii et al., Supercond. Sci. Technol. 25 (2011) 055001.
6:00 AM - I5.9
Non-classical Crystallisation of Cuprate Superconductors
Rebecca H Boston 1 2 3 Simon R Hall 2 Antony Carrington 3
1University of Bristol Bristol United Kingdom2University of Bristol Bristol United Kingdom3University of Bristol Bristol United KingdomShow Abstract
Recent advances in high temperature superconductor (HTSC) synthesis have lead to the creation of a raft of novel morphologies using biopolymers as a means to template crystal growth. In particular, the morphologies created using branched glucan polymers such as dextran have been shown to directly template the crystal growth during calcination to only the areas of the underlying template and nowhere else. We have used dextran to create novel spherical morphologies of yttrium barium copper oxide (YBCO) and bismuth strontium calcium copper oxide (BSCCO) phases. This is the first time that isotropic multi-micron-sized spherical particles of YBCO have been synthesised. Interestingly, despite the non-classical macroscopic form of the superconducting particles, they are crystallographically identical to bulk single crystals. We are able to achieve this morphology through use of beads of a commercially available gel filtration matrix (Sephadex). The beads of Sephadex range from 20-50 Î¼m in diameter and we have shown that the YBCO phase can be templated directly by the beads which are then calcined to leave the perfect YBCO replica. In addition, owing to the outgassing of the dextran during calcination, the spheres are hollow and porous which opens up the possibility for back-filling with a second functional material, thereby allowing us the possibility to explore complementary physico-chemical synergistic effects. On a more immediate level, this novel synthetic route shows a great deal of promise in the rational design of non-classical superconductor morphologies, which may allow us to better address the existing problem of poor grain boundary alignment, which leads to a decrease in critical current and is presently one of the main limiting factors in the application of YBCO-based superconductors.
I1: Pinning of 2G Conductors
Tuesday AM, April 10, 2012