The search for materials with desired magnetic and electrical properties concomitantly relies on the discovery of new systems. To unequivocally determine the compounds&’ innate properties, large single crystals must be grown and characterized. In this talk, I will focus on the versatility and tunability of properties of intermetallics as it applies to the design and discovery of compounds with unusual magnetic and electrical properties. The challenges of phase stability, single crystal growth, structure determination, and physics of these materials will also be discussed.

Alkaline earth metals such as calcium and magnesium are low-melting and reactive toward many elements in the periodic table; this makes them useful as solvents for metal flux reactions. Their melting points can be lowered further by mixing them with other elements; a 50/50 Ca/Li mixture melts at 300 C, and eutectic mixtures of Mg/Al and Ca/Mg both melt at ca. 450 C. Reactions of iron with rare earths and silicon in Mg/Al fluxes produce complex multinary phases including R₅Mg₅Fe₄Al₁₂Si₆, R₃FeAl_4-xMg_xSi₂, and RFe₂Al_7-xMg_x (R = rare earth). All of these structures feature a similar building block of chains of face-sharing aluminum trigonal prisms which are centered by iron. Pseudo-Zintl phases such as CaMgSi and EuMgSn can also be grown in this flux; these compounds are close to a metal-insulator transition and exhibit interesting properties such as magnetoresistance. Calcium-rich fluxes are excellent solvents for carbon and CaH₂, enabling the formation of complex metal carbides and hydrides. These products range from charge-balanced salt-like Ca₁₁Sn₃C₈ and LiCa₂C₃H to phases incorporating a range of hydride and/or carbide interstitials, such as Ca₄₈In₁₃C_4-xH_23+x.

Topochemical reactions can be utilized to direct structure and properties in various compounds. Recent efforts in our group have involved the insertion of cation and/or anion species into layered perovskites via oxidative/reductive intercalation and/or ion exchange. In one case, we have found that the use of reductive intercalation with alkali metals, followed by oxidative intercalation with chalcogen hydride gases, allows for the construction of alkali-metal chalcogen hydride layers within Dion-Jacobson-type hosts; layered perovskites like RbLaNb2O7 can be manipulated to introduce Rb-ChH layers (ChH = OH, SH) within the interlayer. In other systems, two-for-one ion exchange reactions can be carried out on Ruddlesden-Popper perovskites; reactions of K2SrTa2O7 with divalent transition metal ions result in compounds of the form, MSrTa2O7 (M = Co, Zn). Details on the synthesis and characterization of these products will be presented with a discussion on the utility of these set of reactions for manipulations of other solids.

Development of new routes to magnetic materials is a crucial step for the next generation of energy solutions. Besides the energy savings upon synthesis, low temperature methods significantly enhance the capabilities of fine tuning of the structure and properties of a magnetic material. A recent example is an intercalation of Li-ammonia or Li-pyridine into interlayer space of FeSe superconductor, which leads to the significant increase of the superconducting transition temperature. Products of the Li-amines intercalation into pre-synthesized FeSe are fine powders with low degree of crystallinity. Temperatures of conventional solid state synthesis of FeSe (> 1000 K) are not compatible with organic amines. We have developed low temperature (T < 500 K) synthetic route to iron chalcogenides, FeQ (Q = S, Se, Te). The developed method allows us to modify crystal structure of layered FeQ chalcogenides by means of the intercalation of iron-amino complexes. Unlike traditional intercalation techniques, high quality single crystals were obtained, thus facilitating determination of the crystal structure and evaluation of the properties of the synthesized compounds. Synthesis of new materials, their crystal and electronic structure as well as magnetic properties will be discussed.

Our ability to design new materials with desired electrochemical, thermoelectric or strongly-correlated electron properties is limited by thermodynamic control over reaction products in traditional high-temperature synthetic procedures. On the contrary, topotactic reactions, where extensive parts of the original framework are retained, allow for greater control of the structure of the final products; therefore, a combination of desired structural features, spin and oxidation states can be produced in a final material in a predictable fashion.
A 'chimie douce' solvothermal reduction method was developed for topotactic oxygen deintercalation of complex metal oxides. The reduction of the Ruddlesden-Popper nickelate La₄Ni₃O₁₀ was used as a test case to prove the validity of the method. The completely reduced phase La₄Ni₃O₈ was produced via the solvothermal technique at 150°C - a lower temperature than by other more conventional solid state oxygen deintercalation methods. Unlike other techniques, a pure Ni¹⁺ compound, LaNiO₂, can be prepared by solvothermal reduction, demonstrating the advantages of the developed method for synthesis of highly metastable reduced compounds.
Metastable oxyfluorides SrFeO₂F and La₄Ni₃O₈F₂ were prepared through a low temperature, multistep synthesis via fluorination of the infinite layer intermediate phases. Influence of the synthetic pathway on O/F short range ordering and physical properties will be discussed. Mossbauer spectroscopy measurements revealed the predominance of cis fluorine configuration in FeO₄F₂ polyhedra, confirming a difference in local Fe coordination in comparison with O/F disordered SrFeO₂F.
When trying to achieve anion ordering during synthesis, it is important to perform anion intercalation at as low a temperature as possible to avoid thermal randomization of the anions. A low temperature solvothermal fluorination technique, which we developed, allows for fast and facile synthesis at lower temperatures than gas- solid fluorination by XeF₂.
In all known compounds with the alpha-NaFeO₂ structure transition metals oxidation states are either 3+ or 3+/4+. We have developed an “aliovalent exchange plus intercalation” multistep soft chemistry approach for the preparation of a series of new layered transition metal oxides. The synthetic procedure resulted in compounds with the alpha-NaFeO₂ type structures and, uniquely, with transition metals in mixed valent 2+/3+ oxidation states. The oxidation state in the final compounds can be controlled by utilizing A_xMO₂ precursor phase with different x. Crystal structures and physical properties of these novel compounds will be presented.

The structures of the metal-cyanide layers within the group 10 compounds Ni(CN)2, Pd(CN)2 and Pt(CN)2, which consist of vertex-sharing square-planar M(CN)4 units, have recently been determined in detail using total neutron diffraction and will be discussed. Moving to group 11, the binary cyanide, Cu(CN)2, is not known to exist. However, we show here that copper(II) can be stabilised in a cyanide-only environment in the stoichiometric, mixed copper-nickel cyanide, CuNi(CN)4, and in the solid-solution, Cu1-xNi1+x(CN)4 (½ le; x < 1).
The atomic structure of the layers in CuNi(CN)4 and the stacking relationship between nearest-neighbour layers have been determined from total neutron diffraction studies at 10 and 300 K. The structure consists of flat layers of perfectly square-planar [Ni(CN)4] and [Cu(NC)4] units linked by shared cyanide groups i.e. both the metal and cyanide groups are perfectly ordered with Cu(II) coordinated to the nitrogen end of the cyanide group and Ni(II) to the carbon end. It is rather unusual to find Cu(II) in a square-planar environment within an extended solid. The layered structure of this new mixed-metal cyanide is closely related to those of Ni(CN)2, which forms more extended sheets, and Pd(CN)2.xNH3 and Pt(CN)2.xH2O, which form as nanocrystalline materials.
The overall appearance of the powder X-ray diffraction pattern of CuNi(CN)4, including the unusual peak shapes of the observed Bragg reflections, has been successfully explained using models incorporating stacking disorder between next nearest neighbour layers. CuNi(CN)4 shows similar thermal expansion behaviour to that observed previously for Ni(CN)2 [1,4] with negative thermal expansion within the layers (αa = -9.7 MK-1) and positive thermal expansion between the layers (αc = +89 MK-1) measured over the temperature range 200-540 K.
The stability of Cu(II) atoms in a cyanide-only environment has been investigated by varying the ratio of the Cu2+ and Ni2+ ions used in the synthesis. Using a Cu:Ni ratio of 1:1, the anhydrous phase, CuNi(CN)4, is precipitated directly. For Cu:Ni ratios less than one, hydrates of the form Cu1-xNi1+x(CN)4.yH2O (½ le; x < 1; y le; 6) are produced which can be dehydrated to form the corresponding anhydrous compounds, Cu1-xNi1+x(CN)4. These compounds readily rehydrate. Replacement of Cu2+ by Ni2+, which occurs when the Cu:Ni ratio is less than one, leads to the creation of [Ni(NC)4] units. These in turn readily hydrate to form six-coordinated [Ni(NC)4(H2O)2] groups similar to those found in nickel-cyanide hydrates, such as Ni(CN)2.3H2O. [Ni(CN)4] units do not hydrate; hence CuNi(CN)4, which contains such units, is not found in a hydrated form. With Cu:Ni ratios above one, partial reduction of the Cu(II) occurs to form LT-CuCN, in addition to CuNi(CN)4. This result further confirms that Cu(II) ions can only be stabilised when connected to the nitrogen ends of bridging cyanide

The discovery of giant magnetocaloric effect (MCE) in rare-earth and transition metal based materials and prototype equipment development has sparked great interest for magnetic cooling technology. This has also made it a promising alternative to the current vapor compression technology. However, significant synthetic challenges for industrial scale production of MCE materials exist for the successful commercialization of this technology.
We have focused our research activities on the Mn_xFe_2minus;xP_ySi_1-y family of magnetocaloric materials which shows great promise due to their large magnetocaloric properties as a result of being first-order phase transition materials (Tegus et al. 2002, Thanh et al. 2008). Additionally, they exhibit tunable Curie temperatures and earth abundant constituent raw materials. Moreover, they possess excellent long-term stability and their ability to be formed into complex shapes. In this presentation, we will discuss some of the challenges encountered during the up-scaled production of these materials, and how these have been overcome using industrial synthetic routes (for e.g. meltspinning and atomization) in addition to more traditional academic ball milling approach. We will also discuss the magnetocaloric properties of the obtained materials and the performance of these materials during magnetocaloric cycling.
REFERENCES
Tegus, O.; Brück, E.; Buschow, K.; de Boer, F., Transition-metal-based magnetic refrigerants for room-temperature applications, Nature2002, 415, 150.
Thanh, D.; Brück, E.; Trung, N.; Klaasse, J.; Buschow, K.; Ou, Z.; Tegus, O.; Caron, L., Structure, magnetism and magnetocaloric properties of MnFeP1-xSix compounds, J. Appl. Phys.2008, 103, 07B318.

Accommodation of excess oxygen in CeO₂, ThO₂ and UO₂ has been investigated using ab-initio modelling. Hyperstoichiometry was preferentially accommodated by the formation of peroxide species in CeO₂, ThO₂ but not in UO₂, where oxygen interstitial defects are dominant. Migration of the excess oxygen defects was also studied; the peroxide ion in CeO₂ and ThO₂ is transported via a different mechanism to the oxygen interstitial in UO₂. Formation of Frenkel defects was investigated to understand the eect of a peroxide formation on the drive for defect recombination. The presence of the Frenkel vacancy in proximity to the associated additional oxygen defect induces the oxygen to take up an interstitial site, similar to excess oxygen defects in UO₂ rather than remain part of a peroxide molecule.

Mn-doped CeO2 electrolytes were prepared using a soft chemical technique which involved co-precipitation of Mn2+ and Ce4+ using oxalic acid as the precipitant. The incorporation of MnO into ceria lattice was found to be pH dependant. A wider solubility range of managanese dopant concentration into ceria lattice prepared via this method is highlighted. The resultant powders of Mn-doped CeO2 solid solutions, formulated as Ce1-xMnxO2-x, (0.05 le; x le; 0.25), were investigated thoroughly for the first time, from the aspect of synthesis where pH was precisely controlled and varied from 5 - 11. The optimized pH for a stable incorporation of Mn dopant into ceria was found to be pH = 10, in order to obtain the correct stoichiometric compound. The solubility limit of MnO in the CeO2 fluorite lattice structure was suggested to be x = 0.20. The phase composition, morphology properties and elemental analysis of the oxalate and derived-powder was characterized using X-ray diffraction, DTA/TG, SEM and X-ray fluorescence (XRF) respectively. The grain size decreases with increase of MnO content. The electrical conductivity of sintered samples of Mn-doped CeO2 ceramics were investigated in air as a function at 473 - 1073 K using AC impedance spectroscopy. The contributions of the bulk (grain interior), the grain boundary and the electrode polarization behaviour are well documented. The bulk conductivities of the Mn-doped CeO2 ceramics sintered at 1473 K at a test temperature of 1073 K were determined to be 4.223 x 10-4 S cm-1 for Mn content x = 0.10 with activation energy, Ea = 0.88 eV.

Magnetic ceramic nanoparticles of the type xIn2O3-(1-x)alpha-Fe2O3, xV2O5-(1-x)alpha-Fe2O3 and xZnO-(1-x)alpha-Fe2O3 (x=0.1-0.7) were synthesized from the mixed oxides using mechanochemical activation for 0-12 hours. X-ray diffraction was used to derive the phase content, lattice constants and particle size information as function of ball milling time. Mossbauer spectroscopy results correlated with In3+, V5+ and Zn2+ substitution of Fe3+ in the hematite lattice. SEM/EDS measurements revealed that the mechanochemical activation by ball milling produced systems with a wide range of particle size distribution, from nanometer particles to micrometer agglomerates, but with a uniform distribution of the elements. Simultaneous DSC-TGA investigations up to 800 degrees C provided information on the heat flow, weight loss and the enthalpy of transformation in the systems under investigation. This study demonstrates the formation of a nanostructured solid solution for the indium oxide, an iron vanadate (FeVO4) for the vanadium oxide, and of the zinc ferrite (ZnFe2O4) for the zinc oxide. The transformation pathway for each case can be related to the oxidation state of the metallic specie of the oxide used in connection with hematite.
NSF-DMR-0854794

Metal-Organic Frameworks (MOFs) have gained a tremendous amount of attention in the past few decades. Due to the tunable nature of their ligand geometry, their enormous surface area and their large gas uptake capacities, MOFs are widely applied in many areas such as gas storage, gas separation, CO2 capture, catalysis, drug delivery, sensors, photosensitive materials and magnetic materials. However; it is still problematic to construct MOFs with large porosity, high stability and good crystal quality, while many potential MOF applications require them to possess those properties simultaneously. Typically, in order to attain larger pore sizes and surface areas, researchers attempt elongation of MOF constructional units. However, this will often inherently undermine the framework stability and crystallinity and increase the possibility of framework interpenetration. Additionally, recent research indicates that the crystal size, quality and morphology can largely affect the surface area of the resulting MOFs.
The MOFs based on the ultrastable zirconium polyoxo clusters have demonstrated their excellent stability toward air, water, or even concentrated acid. Even though a limited number of Zr MOFs were published, many of them suffer from a low crystallinity and limited pore sizes. In this work, a series of non-interpenetrated zirconium MOFs were synthesized from a group of tetrahedral ligands via a modulated synthesis strategy. All of them possess new MOF topologies, large cavities and high crystal quality. Two categories of polymorphic MOFs can be identified and their isostructural MOFs were obtained by using elongated analogous ligands. Remarkably, PCN-525 has largest surface area, pore size (up to 25Å) and solvent accessible volume (up to 84.10%) among all the MOFs constructed from tetrahedral ligands. It is one of the rare examples of mesoporous Zr MOFs with three dimensional channels. PCN-522 is the first MOF that contains two distinctive Zr-based clusters, which has an unprecedented 4, 12, 12-connected topology that incorporates tetrahedra, cuboctahedra and icosahedra in the same network. This work provides both insights into novel framework topologies with tetrahedral building units and a practical method of constructing MOFs with large pore size and high stability.

Multifunctional materials combine more than one imaging modality such as optical imaging, X-ray computed tomography (CT), positron emission tomography (PET), and magnetic resonance (MR) imaging contained in single vehicle. In particular, optical imaging provides its high resolution in bio-imaging and MR imaging offers excellent anatomical depth, non-invasive, and real time monitoring. Thus, a lot of attentions had been paid to the development for the multifunctional nanomaterials combining the two representative modalities such as optical and MR imaging, especially for application in biomedical applications.
It is worth noting that lanthanide-doped (Ln3+) nanoparticles serves as an alternative to conventional luminescent labels such as organic dye, QDs for application in biological medical imaging due to its advantageous characteristics such as low toxicity, high resistance to photo-bleaching and photochemical degradation. Moreover, the luminescence features of lanthanide ions also include high quantum yield, large stoke shift, abundant energy level transitions, narrow emission band width, and long fluorescent life time.
In recent, Gd3+-based inorganic nanomaterials has attracted much interest because they could be used as potential multifunctional platform. It was well known that a paramagnetic nature of Gd3+ ion arising from seven unpaired electrons in 4f electron shell could be utilized as contrast agents for T1-enhanced MR imaging owing to their enhancement of relaxation of the neighboring protons. In addition, by doping light-emitting various lanthanide ions (Ln3+) into a Gd3+-containing host matrix, novel materials possessing both advantages of fluorescent and magnetic properties could be achievable for multimodal imaging. For the research of optical imaging on the multifunctional GdPO4 nanoparticles, the research has been extensively studied only in visible range. There have been no reports on multifunctional GdPO4 nanoparticles having both UV emission and MR properties, which could be potentially used as alternative multifunctional nanoprobes. The understanding of optical properties of Ce3+, Pr3+ and Gd3+, having electronic configuration in UV spectral domain in inorganic compounds is of great important due to the potential technological applications as imaging, lithography, and optical data recording. Thus, nanoparticles with both UV emission and magnetic resonance properties could open new area of biomedical technology.
In this report, we present a general strategy for the synthesis of GdPO4 nanorods and nanoparticles doped with Ln3+ (Ln3+ = Ce3+, Pr3+) having strong UV emission and magnetic property. We explain multifunctional property change when crystal phase and structure change from hexagonal GdPO4 nanorods to monoclinic GdPO4 nanoparticle after calcination at 900 degrees Celcius , which could be potentially applied as MR imaging contrast agent.

Thermochromic smart film, typically based on VO2 nanoparticles, has received particular interest because it can intelligently modulate the amount of near-infrared ray by changing from transparent state at low temperature to reflective state at high temperature, while maintaining visible transmittance. This film is promising for application in building and automotive glasses to increase energy efficiency.
In this study, we demonstrated that hydrothermal process used to prepare metal-doped VO2(M) nanopowder with a special emphasis on calcination condition and novel solution process used to prepare transparent, stable and flexible VO2(M) based film. Monoclinic VO2(M) nanopowder was obtained from vanadium pentoxide and oxalic acid by controlling hydrothermal and calcination conditions. By further increasing calcinations temperature to about 700°C for 2 h with N2 gas during calcinations step, VO2(A) was transformed only to VO2(M). Due to the small band gap between VO2(A) and rutile-type VO2(M), VO2(A) would directly be transferred to stable VO2(M). Metal doping led to decrease phase-transition temperature from 68°C to 35°C. Metal-doped VO2(M) nanoparticles based film could exhibit a large change of NIR transmittance for phase-transition temperature than bare VO2 based film.

The structure refinement of three decagonal phases: Al-Cu-Co, Al-Cu-Rh, Al-Cu-Ir will be presented [1]. The synchrotron diffraction experiments were performed at the Swiss - Norwegian beam line at ESRF, Grenoble, France. All three decagonal phases show ~4 Å periodicity (two atomic layers per period). A computer program SUPERFLIP [2], based on the charge-flipping algorithm, was used for the initial phasing of the data and obtaining the electron density maps. These maps were used for deriving a Rhombic Penrose Tiling (RPT) model with a tiling edge-length of ~17 Å. The decoration of the unit tiles is based on the ~33 Å cluster proposed by Hiraga & Oshuna [3]. The decoration of RPT with Hiraga clusters is such, that the cluster centers form the Pentagonal Penrose Tiling of an edge-length of ~20 Å. The Hiraga cluster can be considered as a supercluster built of 5 clusters proposed by Deloudi et al. [4]. Such a structure explains well the strong Patterson peaks of ~ 12 Å, ~20 Å, and ~32 Å occurring for all three phases. The structure refinement was performed in the real space using the so-called Average Unit Cell approach. This method allows a purely 3D optimization of a quasicrystalline structure and has been previously used for a variety of decagonal pahses in the Al-Ni-Co system [5-7]. Our work shows the first solution of a quasicrystal as a ternary alloy (Rh and Ir phases). The final R-values are reasonable, the structure is consistent with TEM images and the chemical composition agrees well with the EDX measurements.
References
[1] P. Kuczera, J. Wolny, W. Steurer, Acta Crystallogr. B 68 (2012) 578.
[2] L. Palatinus, G. Chapuis, J. Appl. Crystallogr. 40 (2007), 786.
[2] K. Hiraga, T. Ohsuna, K.T. Park, Phil. Mag. Lett. 81 (2001), 117.
[4] S. Deloudi, F. Fleischer, W. Steurer, Acta. Crystallogr. B 67 (2011), 1.
[5] P. Kuczera, J. Wolny, F. Fleischer, W. Steurer, Philos. Mag. 91 (2011), 2500.
[6] P. Kuczera, B. Kozakowski, J. Wolny, W. Steurer, J. Phys. Conf. Ser. 226 (2010), 012001.
[7] J. Wolny, B. Kozakowski, P. Kuczera, H. Takakura, Z. Kristallogr. 223 (2008), 847.

A piezoelectric ceramic Pb(Ti_1-xZr_x)O₃ (PZT) is widely used for various applications such as transducer and sensors. PZT shows a maximum piezoelectric property at composition around x = 0.5, the boundary separating the tetragonal (Ti-rich) and the rhombohedral (Zr-rich) phases in the phase diagram. This boundary is known as a morphotropic phase boundary (MPB). The origin of the enhanced piezoelectric property at MPB is explained as follows. There exist a monoclinic phase with a radic;2a × radic;2a × a unit cell where a was the cubic perovskite lattice parameter, and Cm symmetry at MPB composition at low temperature. The lack of symmetry axis in the monoclinic structure allows the rotation of the ferroelectric polarization vector between the polar axes of the tetragonal and the rhombohedral phases. Such a polarization rotation is induced by application of electric filed leading to the enhancement of the piezoelectric constant. However, the polarization rotation has never been observed experimentally.
In this study, we show the presence of polarization rotation in BiCo_1-xFe_xO₃ (x ~ 0.7). BiCoO₃-BiFeO₃ system attracts attention as a candidate lead-free piezoelectric material because of the similarity of the phase diagram to that of PZT. The crystal structure as determined by powder synchrotron X-ray diffraction (SXRD) was the same as that of the low temperature phase of PZT at the MPB. Composition and temperature induced second order structural transition from tetragonal to monoclinic structures was observed. The structural change was accompanied by a rotation of the polarization vector from [001] to [111] directions of a pseudo cubic cell. This is the first observation of the polarization rotation in a monoclinic perovskite.

PbCrO3 had long been considered as a boring antiferromagnetic cubic perovskite. However, the lattice constant of 4.01Å is considerably larger than that of Sr2+Cr4+O3 and Cr3+ is expected from bond valence sum. Furthermore, pressure induced volume collapse of 9% was recently found[1]. To clarify its mysterious nature we prepared pure PbCrO3 and Pb1-xSrxCrO3 samples, and systemically studied their physical properties. The temperature dependence of paramagnetic susceptibility indicated that the actual valence of Cr is +3 for pure PbCrO3, contrarily to +4 for Cr of the previous reports [2]. Meanwhile a pressure induced insulator to metal phase transition was observed for PbCrO3 around 3GPa, which should be attributed to the electronic configuration change of Cr from t2g3 to t2g2. We thus proposed a new oxidation state of Pb2+0.5Pb4+0.5CrO3 like Bi3+0.5Bi5+0.5NiO3 [3] with disordered arrangement of Pb2+ and Pb4+ which was confirmed by X-ray photoelectron spectroscopy (XPS). An intermetallic charge transfer between Pb4+ and Cr3+ leads to the Pb2+Cr4+O3 state under pressure. A distinct volume drop was found for Pb1-xSrxCrO3 at around x=0.3 where insulator to metal phase transition was also observed, suggesting the valence change of Cr ion from 3+ to 4+ which was confirmed by O-K edge X-ray absorption spectroscopy(XAS). Based on the above results we believe that charge transfer between Pb and Cr takes place in both PbCrO3 and Pb1-xSrxCrO3 under pressure and by Sr substitution, respectively.
[1] W. Xiao et al., PNAS 107, 14026 (2010).
[2] A. M. Arévalo-Loacute;pez et al., Inorg. Chem. 48, 5434 (2009).
[3] M. Azuma et al., Nat. Commun. 2, 347 (2011).

Materials with the CuFeO2 structure are of great interest as transparent conducting oxides [1] and for their exotic magnetism. This layered structure consists of sheets of edge-sharing metal-oxygen octahedra separated by group IB metals with a dumbbell coordination. Two stacking polytypes are commonly found - the 3R and 2H - and often samples contain a mixture of the two, making the interpretation of the properties difficult.[1]
A variation of the CuFeO2 structure is found in some cases where two different B cations form an ordered honeycomb lattice in the sheets of edge-sharing octahedra. The honeycomb lattice is of interest to the magnetism community as a frustrated X-Y system, and as a spin-liquid candidate when strong spin-orbit coupling is present, such as in Na2IrO3.[2]
Here we describe our results on the 2H polytypes of Cu3Ni2SbO6 and Cu3Co2SbO6 formed by a high temperature synthesis route.[3] Synchrotron powder X-ray diffraction, neutron powder diffraction data and high resolution transmission electron microscopy are used to resolve atomic and magnetic structures of the materials. In addition, synthesis of the 3R polytypes has been accomplished by low temperature cation exchange. Their structures and properties will be compared to the 2H polytypes.
[1] M.A. Marquardt, N.A. Ashmore, D.P. Cann, Thin Solid Films 496 (2006) 146-156.
[2] Y. Singh, P. Gegenwart, Physical Review B 82 (2010) 064412.
[3] J.H. Roudebush, N.H. Andersen, R. Ramlau, V.O. Garlea, R. Toft-Petersen, P. Norby, R. Schneider, J.N. Hay, R.J. Cava, Inorganic Chemistry (2013).

Lanthanum germanate and silicate (La9.33+x(MO4)6O2+1.5x, M=Ge or Si) with an apatite-type crystal structure are promising oxide-ion conductors for electrolytes of solid oxide fuel cells. It was reported that mobile interstitial oxide ions are introduced in the case of x > 0 with increasing ionic conductivity, and it is thus important to understand its oxide-ion conduction mechanism on an atomic level. For this purpose, the conduction mechanisms in lanthanum germanate and silicate have theoretically been investigated in the present study. Specifically, the stable sites of interstitial oxide ions in the crystals and the potential barriers of conduction pathways connecting the stable sites were clarified in a first-principles manner based on the projector augmented wave method.
Regarding the obtained stable sites of interstitial oxide ions, they are located between neighboring two GeO4 tetrahedra in lanthanum germanate. On the other hand, in lanthanum silicate, the similar sites between SiO4 tetrahedra are metastable sites, and the most stable sites are located at the periphery of the O4 column. During the oxide-ion conduction, cooperative migration processes involving several oxide ions at interstitial and neighboring regular sites, i.e., the interstitialcy mechanisms, predominantly occur in these two systems, rather than the simple interstitial mechanisms. In lanthanum germanate, cooperative oxide-ion conduction processes around GeO4 tetrahedra along the c axis are dominant for the long-range migration. On the other hand, in lanthanum silicate, the estimated potential barrier of the cooperative conduction in the O4 column along the c axis was less than 0.1 eV, which is much lower than the apparent activation energy reported experimentally (0.4-0.9 eV). This is probably because the interactions between interstitial oxide ions closely-arranged along the c axis in the O4 column are not taken into consideration. This implies the migration processes between the most stable and metastable sites should be the key to determine the conductivity curve in the silicate. Thus, there is the significant difference in oxide-ion conduction mechanism between the two systems, which reflects the difference in the stable sites despite the same apatite-type crystal structure.

Many classes of proton-conducting oxides have been reported so far, e.g., perovskite-type, fluorite-type, pyrochlore-type, monazite-type, and their related oxides. According to the conventional view, protons in such the oxides reside and rotate around oxide ions with OH bonds and sometimes hop into neighboring oxide ions (rotations and hoppings). Geometries of oxygen polyhedra in the crystals are, therefore, key factors in the proton conductivities. In the present study, we have theoretically analyzed proton conduction mechanisms in several types of oxides from first principles, to clarify the roles of the oxygen polyhedral network in the crystals.
All the first-principles calculations were based on the projector augmented wave method implemented in the VASP code. Local energy minima in the crystals (proton sites) were determined by construction of the potential energy surfaces of a proton with the fixed atomic positions and the subsequent structural optimizations. Proton conduction paths were evaluated using the nudged elastic band method, and the kinetic Monte Carlo simulations were finally performed to estimate the proton diffusivity and conductivity.
First, concerning the proton sites in oxides, protons were found to prefer non-shared oxide ions to corner-shared oxide ions in oxides to form an OH bond. This trend appears prominently in oxides having lower-coordinated oxygen polyhedra, which implies that the positive charges of cations at the centers of polyhedra not perfectly screened by coordinated oxide ions lead to the comparatively high potential energy in the vicinity of corner-shared oxide ions with two neighboring cations. Thus, corner-shared oxide ions seem to have no direct contribution to the proton conduction in oxides.
Note here that protons are further stabilized by hydrogen bonds (OH-O bonds) formation in addition to the OH bonds. The distances from the second-nearest-neighbor (2NN) oxide ions are also short (< 1.7 Å), which are comparable to those in ice and water. In other words, proton incorporation in oxides can be rephrased as hydrogen bond formation. Furthermore, proton conduction in oxides can be regarded as repetition of forming and breaking the hydrogen bond, i.e., hydrogen bond switching, which is a new picture of proton conduction in oxides in place of rotations and hoppings. Corner-shared oxide ions are involved in the hydrogen bond formation and switching as the 2NN oxide ions, and not directly but indirectly contribute the proton conduction in oxides. In addition, the corner-sharing of oxygen polyhedra plays a role in reducing the distances among non-shared oxide ions, which can provide fast proton migration paths in the connection direction. Actually, the present study found fast proton conduction channels along infinite oxygen polyhedral chains in La₃NbO₇ and LaP₃O₉, leading to their large anisotropic proton diffusivities and conductivities.

The solid-state reaction of thin film metals on germanium substrates is used to form low sheet resistance germanide layers and low resistance contacts for germanium semiconductor devices, similar to the formation and use of silicides in silicon devices. Nickel germanide is the most promising germanide for use in germanium contacts because it has low resistivity (15mu;Omega;.cm) and low temperature of formation. In this study we examine the thermal budget, investigating the lowest temperature of formation that can be used. Results show that temperatures less than 300 C can be used to form NiGe but temperature duration is significantly longer than for higher temperatures. At temperatures less than 200 C, NiGe does not form.
X-Ray Photoelectron Spectroscopy and X-Ray Diffraction were used to examine the stoichiometry and structure of the germanides formed and cross-section Transmission Electron Microscopy was used to show the texture of the germanide layer and in particular the texture and constituent atoms of the germanide to germanium interface. These results show that the germanide formed is very close to NiGe (1:1), the surface roughness (approximately 4nm) is only slightly greater than the polished Ge wafer, grain sizes approximately 100nm in dimension and the roughness of the NiGe to Ge interface is significantly high at approximately 30nm. As suggested by the interface roughness, the grain heights for the formed NiGe grains varies from approximately 1.9 times to 2.4 times the original Ni thickness. Oxygen contamination is evident at the germanide-germanium interface using TEM element mapping, but does not occur in the germanide material. The roughness of the germanide-germanium intercface was determined by selective etching of the germanide and using an atomic force microscope to determine the roughness of the exposed germanium surface.
The electrical properties of the germanides formed were determined using the Van der Pauw technique and using a novel test structure to determine the interface specific contact resistance between the NiGe and germanium substrate.
The solid state reactions were done on a resistive heat stage in a nitrogen environment. Completion of reaction for the Ni thicknesses used (50 nm to 500nm) was determined using XRD and sheet resistance measurements. The solid state reaction was also examined using a heat stage with situ XRD taking measurements.

Antimony oxides are widely used as oxidation catalysts, optoelectronic, and magnetic materials[1]. Its amorphous phase has also been attracting much attention due to its potential use in advanced optical devices[2]. Antimony oxides come in a wide range of stoichiometry and polymorphs, namely α-Sb₂O₃, β-Sb₂O₃, γ-Sb₂O₃, α-SbO₂, β-SbO₂ and Sb₂O₅, arising from the existence of various possible oxidation states of antimony. There have been rigorous efforts to synthesize and characterize these oxide phases[3], however, currently the microscopic fundamental understanding is still lacking. This is especially so for the local ordering of its amorphous phase. In this work, we employ first-principles based density-functional theory calculations and ab-initio molecular dynamics to study the crystalline and amorphous phase of these oxide polymorphs, detailing their energetics, atomic, and electronic structure. This preliminary study provides a platform for our future work on studying the use of antimony oxide nanostructures in advanced coatings and optical devices.
[1] H. S. Chin, K. Y. Cheong, and K. A. Razak, J. Mater. Sci. 45, 5993 (2010).
[2] K. Terashima, T. Hashimoto, T. Uchino, S.-H. Kim, and T. Yoko, J. Ceram. Soc. Jpn.104, 1011 (1996).
[3] D. Orosel, R. E. Dinnebier, V. A. Blatov, and M. Jansen, Acta Crystallogr. B68, 1 (2012)

CuCr2Se4 is a room temperature ferromagnet and metallic conductor [1-2]. It crystallizes in spinel type structure, the space group Fd m with lattice parameter a = 1.03340 nm [3] and has a normal cation distribution. The copper ions occupy tetrahedral Wyckoff site 8a and the chromium ions trigonal antiprismatic (usually called octahedral) site 16d. The ease of doping, usually in a large concentration range, has already been exploited for renewable energy [4].
CuCr2Se4 single crystals doped with ytterbium were obtained using chemical vapour transport method. Binary selenides CuSe and Yb2Se3 were used as the starting materials and anhydrous chromium chloride CrCl3 was a transporting agent. The crystallization process was carried out in quartz ampoules and in horizontal temperature zonal furnace. The weighs were prepared with the assumption that ytterbium would substitute chromium, according to the reaction:
(4-2.25) CuSe + 0.75 Yb2Se3 + (2-x) CrCl3 → Cu[Cr2-xYbx]Se4 + CuCl2 + YbCl3 for x=0.1; 0.25, 0.5. The well-shaped octahedral single crystals were chosen for further investigations. First chemical composition was determined using energy-dispersive X-ray fluorescence spectrometer (EDXRF). It was established that amount of ytterbium admixture is about half of weight percentage.
Dynamic (ac) magnetic susceptibility was measured in the temperature range 4.2-300 K and at an internal oscillating magnetic field Hac = 3.9 Oe with an internal frequency f = 300 Hz. Magnetization was measured in the magnetic field Hdc = 0.5, 1.0, 5.0 and 10.0 kOe and recorded both in zero-field-cooled (ZFC) and field-cooled (FC) mode. Magnetization isotherms were measured at 4.2 K and at 300 K in the static magnetic field up to 70 kOe. For that purposes a Quantum Design System (MPMS XL) was used. Static (dc) magnetic susceptibility was measured using a Faraday type Cahn RG automatic electrobalance up to 600 K. The most spectacular observation is that for small amount of chromium and ytterbium both the real and imaginary components of the magnetic susceptibility are oscillating around the value zero and the FC-ZFC splitting suggests the diamagnetic frustration while for larger Cr and Yb-content a ferrimagnetic state occurs.
Acknowledgements
This paper is funded from science resources for years 2011-2014 as a research project (project No. N N204 151940).
[1] G.J. Synder, T. Caillat, and J.P. Fleurial, Mat. Res. Inn. 67, 5 (2001).
[2] A. Payer, R. Schoellhorn, C. Ritter, and W. Paulus, J. All. Comp. 191, 37 (1993) .
[3] I. Okonska-Kozlowska, J. Kopyczok, H.D. Lutz, and Th. Stingl, Acta Cryst. C49, 448 (1993).
[4] G.J. Synder, T. Caillat, and J.P. Fleurial, Phys. Rev. B 62, 10185 (2000).

Spontaneous polarization enhancement or stable ferroelectric phases in incipient ferroelectrics have been theoretically predicted for nanowires and nanoparticles [1,2]. In this work, the possibility of nanosize induced ferroelecticity in CaTiO3 nanocrystals is studied by using second harmonic (SH) generation, photoluminescence and Raman spectroscopy as a function of temperature. The CaTiO3 nanoparticles (40nm to 50nm size) were grown by solid-state reaction [3] and sol-gel techniques [4] and verified the single-phase composition by XRD and TEM.
Experimental evidence of nanosize induced symmetry lowering in CaTiO3 perovskite nanocrystals are reported. More specifically, we show how the generated SH response from CaTiO3 nanocrystals vanishes upon heating at around 380 K and recovers when the system is cooled down. Thus, even though the lack of inversion symmetry required for SHG may be relaxed at nanoparticle surfaces, the presence of a well-defined Tc indicates that the system undergoes through a structural transition involving a symmetry reduction (non-centrosymmetric) in the crystal structure. This transition is confirmed by Raman spectroscopy, as manifested by the softening observed for low frequency modes at similar temperatures. Density Functional Theory (DFT) and empirical potential modeling shows a surface reconstruction and suppression of octahedral rotations as the origin of this ferroelectric behavior.
[1] S. Li and K. Rabe, Am. Phys. Soc, APS March Meeting. Abstract # S.20.011 (2007)
[2] A. N. Morozovska et al. Phys. Rev. B, 76, 014102 (2007)
[3] J. Li et. al., Mat. Lett, 65, 1556-1558 (2011)
[4] K. Lemanski et. al., J. Sol. State Chem., 184, 10 (2011)

The normal spinel ZnCr2Se4 (SG 227, a=10.489Å) is a semiconductor with high positive paramagnetic Curie-Weiss temperature (115 K), which orders magnetically at 21K into a spiral structure. The magnetism is governed by the balance between ferromagnetic Cr-Se-Cr superexchange and numerous next neighbor antiferromagnetic interactions, which are relatively easy tuned by doping. Numerous useful properties can be generated by a proper selection of dopant like colossal magnetoresistance or increased Seebeck effect. Of a special interest is doping with 4f metals due to their high localized magnetic moment.
Our investigations aim to describe how the introduction of dysprosium and neodymium changes the basis properties of the matrix.
The polycrystalline compounds ZnCr1.95Dy0.05Se4 and ZnCr1.95Nd0.05Se4 were prepared by ceramic method according to chemical reactions:
ZnSe + 0.975Cr2Se3 + 0.25Dy2Se3 = ZnCr1.95Dy0.05Se4 (1)
ZnSe + 0.975Cr2Se3 + 0.25Nd2Se3 = ZnCr1.95Nd0.05Se4 (2)
The stoichiometric quantities of binary selenides were sintered twice in silica ampoules for 240h at 1173K. The XRD phase analysis revealed a single spinel phase (space group Fd-3m) up to the detection limit of the method and structural parameters obtained using the Rietveld method.
The chemical compositions of ZnCr1.95Dy0.05Se4 and ZnCr1.95Nd0.05Se4 compounds were measured using scanning electron microscopy. The magnetic properties were determined using high magnetic stationary fields (up to 14 T) and SQUID - magnetometer (0.05 T) in the temperature range 2-300 K and are presented below.
Chemical composition, structural parameters and magnetic properties for ZnCr1.95Dy0.05Se4 and ZnCr1.95Nd0.05Se4 compounds in comparison to the ZnCr2Se4:
Nominal composition: ZnCr1.95Dy0.05Se4, Chemical composition: Zn0.92Cr1.68Dy0.06Se4, a=10.4970(4)A, u=0.25967(5), mu;eff (B.M./f.u.)=5.17, mu;sat(B.M./f.u.)=6.24, ΘCW(K)=66.5, CM(K)=3.34, TN(K)=21.7.
Nominal composition : ZnCr1.95Nd0.05Se4, Chemical composition: Zn0.90Cr1.87Nd0.07Se4.0,
a=10.4978(7)A, u =0.25952(8), mu;eff (B.M./f.u.)=6.73, mu;sat (B.M./f.u.)=6.05, ΘCW(K)=56.4, CM(K)=5.65, TN(K)=25.3.
ZnCr2Se4: a=10.489(7)A, u=0.258, mu;eff (B.M./f.u.) =5.47, mu;sat (B.M./f.u.)=5.74, ΘCW(K)=115, CM(K)=3.54, TN(K)=21.
(a - lattice parameter, u - coordinate of Se)
Neutron powder diffraction of the Nd doped sample confirmed the presence of incommensurate spiral structure with propagation wektor k=0.4715(2) and magnetic moment on B site equal 2.91(3) mu;B.
The local structure around the dopants were analyzed using XANES studies. The results of investigations will be presented on the conference.
Acknowledgement
This study is funded from science resources for years 2011-2014 as a research project (project No. N N204 151940).

Ce³⁺ is known to show broad optical emission peaking in the green spectral range [1]. For the stabilization of 3-valent cerium in ceramic phosphors such as calcium scandate CaSc₂O₄, often codoping with sodium for charge compensation is perform