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A ternary stannide of sodium and magnesium, Na2MgSn, was synthesized from the elements, and the crystal structure was determined by single-crystal X-ray diffraction. The compound crystallizes in the Li2CuAs structure type (hexagonal, P63/mmc, Z = 2, a = 5.0486(11) Å, c = 10.095(2) Å), and its structure is built up of two-dimensional honeycomb layers of 2∞[(MgSn)2-] stacked along the c-axis, with Na atoms as "space fillers". First-principles computations at various levels of density functional theory (DFT) verify that the most stable configuration is the one in which Na and Mg atoms occupy the 4f and 2b sites, respectively, and thus DFT provides a necessary complement to X-ray structural elucidation. Our computations also predict that Na2MgSn must be a semiconductor with a small band gap. In accord with these predictions, the electrical resistivity measured for a polycrystalline sample of Na2MgSn is 9.6-10.4 mΩ cm in the range of 90-635 K, and the Seebeck coefficient decreases from +390 μV K-1 (at 300 K) to +150 μV K-1 (at 430 K). [ABSTRACT FROM AUTHOR]

Abstract: A powder sample of a metastable phase β-MoSi2 having the C40-type crystal structure was prepared by heating Mo sheets with a Na–Si melt at 858 K for 12 h to determine details of the crystal structure. The lattice constants (a = 4.6016(3) Å and c = 6.5700(3) Å) and Si atom coordinate (y = 0.1658(2)) of β-MoSi2 were determined by Rietveld analysis of the X-ray powder diffraction. The thermoelectric properties were refined for a bulk sample prepared by sintering the β-MoSi2 powder at 773 K and 600 MPa. The electrical resistivity of the sintered β-MoSi2 sample with a relative density of 65% of the theoretical one was 2.5 mΩ cm at 300 K, and slightly increased with increasing temperature from 300 to 725 K. The Seebeck coefficients changed from +60 to +89 μV/K in the temperature range from 330 to 725 K. The maximum thermoelectric power factor was 2.2 × 10−6 W cm−1 K−2 at 725 K. [Copyright &y& Elsevier]

A bulk layer of aluminum nitride (AlN) polycrystals was synthesized on a boron nitride crucible surface by heating Al chunks with 5 mol% of bismuth at 1273 K for 3 h under NH3 gas flow. The fragments of the layer were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The platelet grains of AlN with a size of 0.1–1.0 μm and having preferred orientation of the c-axis perpendicular to the layer were formed at the crucible side. Nanotubes 6–15 μm long and about 20–100 nm thick grew on the gas phase side of the layer. [ABSTRACT FROM AUTHOR]

The article reports on the X-ray diffraction, morphology, and thermoelectric properties of magnesium silicide bulk sample prepared by using a compact body of sodium silicon powder and magnesium melt. Details of the preparation of sodium silicon are provided. The thickness of the wall is cited. The sample of magnesium silicide exhibited p-type thermoelectric and semiconducting behavior, which was attributed to sodium doping of less than 0.5 wt% in magnesium silicide.

Abstract: β-FeSi2 was synthesized by heating mixtures of Si and Fe powder sealed with Na metal and Ar gas in a stainless tube. Diffuse streaks elongated along the a axis were observed in the electron diffraction (ED) patterns of β-FeSi2 prepared at 873K in the Na melt. No streaks appeared on the spots indexed by k + l =2n (n: integer), which indicated existence of stacking faults caused by a slip system of (100)[011]/2. The powder X-ray diffraction (XRD) patterns of the samples prepared at 873K for 48h in the Na melt and at 1173K for 24h under reduced Na vapor pressure were analyzed by the Rietveld method with a statistical split-site model based on the stacking fault structure. The powder X-ray diffraction patterns of the samples prepared at 873K for 48h in the Na melt and at 1173K for 24h in Na vapor which evaporated from a mixture of Na and Si were analyzed by the Rietveld method with a statistical split-site model based on the stacking fault structure. The ratios of the normal stacking layer and stacking fault layer of the samples prepared at 873 and 1173K were estimated to be 0.95:0.05 and 0.84:0.16, respectively. Main features of the observed powder X-ray diffraction patterns were well reproduced by the calculation based on a general recursion method for calculating diffracted intensities from crystals containing stacking fault. [Copyright &y& Elsevier]

Abstract: The effects of substrate temperature, T s, on the crystallinity and the electrical properties of Ga-doped ZnO films (GZO) with a thickness of 200 nm were investigated. GZO films were prepared on glass substrates at various T s in the range from 150 to 400 °C by ion-plating method with DC arc discharge. X-ray diffraction analysis reveals that GZO film prepared at 250 °C shows the preferential orientation of c-axis and the highest crystallinity. Williamson–Hall analysis indicates that the crystallite size of GZO films remains nearly constant with increasing T s up to 300 °C, and then, with further increasing T s, decreases gradually. The Ga concentration in the films, estimated by secondary ion mass spectroscopy and X-ray fluorescence analyses, increases monotonically with increasing T s above 250 °C. Hall effect measurements show that resistivity decreases slightly with increasing T s up to 250 °C, leading to the lowest resistivity of 2.1×10−4 Ω cm at 250 °C, and then exhibits a gradual increase with further increasing T s. [Copyright &y& Elsevier]

Compounds in a CaO–Y2O3–SnO2 system were prepared by a solid-state reaction at 1673 K. The phase relation in this system was investigated by powder X-ray diffraction. Besides the previously reported ternary compounds, CaSnO3, Ca2SnO4, Y2Sn2O7, and a quaternary compound Ca0.4Y1.2Sn0.4O3, solid-solution series of Ca2− xY2 xSn1− xO4 with 0≤ x≤0.5, and Ca1− yY2 ySn1− yO3 with 0≤ y≤0.2 and 0.95≤ y≤1.0 were found. The cell parameters of these solid-solution series were refined. The changes of rhombohedral cell parameters in the samples prepared in the range 0.565< y<0.714 of Ca1− y Y2 ySn1− yO3 suggested the existence of solid solutions of Ca0.4Y1.2Sn0.4O3, although their single phases could not be prepared, except at y=0.6. [ABSTRACT FROM AUTHOR]

Abstract: The X-ray powder diffraction pattern of NbSi1.9 prepared by heating Nb and Si powders with Na at 900 K for 48 h in Ar was analyzed by the Rietveld method. The broadening peaks of X-ray reflections suggested stacking faults of the C40 structure. The XRD pattern was simulated with a stacking fault model using DIFFaX. [Copyright &y& Elsevier]

Abstract: Single crystals of iron(II) pyroborate, Fe2B2O5, were prepared at 1000–1050°C under an argon atmosphere. The crystals were transparent, yellowish in color and needle-like or columnar. The crystal structure of Fe2B2O5 was analyzed by single-crystal X-ray diffraction. Refined triclinic unit cell parameters were a=3.2388(2), b=6.1684(5), c=9.3866(8)Å, α=104.613(3)°, β=90.799(2)° and γ=91.731(2)°. The final reliability factors of refinement were R1=0.020 and wR2=0.059 [I > 2σ(I)]. Transmittance over 50% in the visible light region from 500 to 750nm was observed for a single crystal of Fe2B2O5 with a thickness of about 0.3mm. The light absorption edge estimated from a diffuse reflectance spectrum was at around 350nm (3.6eV). Magnetic susceptibility was measured for single crystals at 4–300K. Fe2B2O5 showed antiferromagnetic behavior below the Néel temperature, T N≈70K, and the Weiss temperature was T W=36K. The effective magnetic moment of Fe was 5.3μ B. [Copyright &y& Elsevier]

Abstract: New compounds CaY2Ge3O10 and CaY2Ge4O12 were prepared by heating mixtures of CaCO3, Y2O3 and GeO2 at 1200°C. CaY2Ge3O10 is stable at 1300°C, while CaY2Ge4O12 decomposes into a melt and CaY2Ge3O10 at approximately 1250°C. We obtained single crystals of CaY2Ge3O10 by cooling a sample with an initial composition of Ca:Y:Ge=1:2:8 from 1300°C with a rate of −6°C/h. The crystal structure of CaY2Ge3O10 was determined by single crystal X-ray diffraction. CaY2Ge3O10 crystallizes in the monoclinic space group with , , and , , and for . In the structure of CaY2Ge3O10, Ca and Y atoms are situated disorderly in three 7-fold coordination sites between isolated germanate groups of triple GeO4 tetrahedra, Ge3O10. The structural formula of CaY2Ge3O10 is expressed as (Ca0.45Y0.55)(Ca0.46Y0.54)(Ca0.09Y0.91)Ge3O10. The crystal structure of CaY2Ge4O12 was analyzed by the Rietveld method for the X-ray powder diffraction pattern. CaY2Ge4O12 is isotypic with SrNa2P4O12, crystallizing in the orthorhombic space group P4/nbm, , , , , . CaY2Ge4O12 contains four-membered GeO4-tetrahedra rings, Ge4O12. Eight-fold coordinated square-anitiprism sites and 6-fold octahedral sites between the layers of the Ge4O12 rings are occupied by Y atom and Ca/Y atoms, respectively The structural formula is Y(Ca0.5Y0.5)2Ge4O12. [Copyright &y& Elsevier]

Abstract: Solid solutions of spinel-type cobalt-ruthenium oxides Co3−x Ru x O y (0.50≤ x ≤0.70, y =3.8–3.9) were prepared from Co3O4 and RuO2 powders by solid-state reaction at 1173–1273K in air. The crystal structures of the solid solutions were refined by Rietveld analysis of powder X-ray diffraction (XRD) patterns. The solid solutions crystallized in cubic cells (space group: ) with formal compositions of (Co)tet[Co2−x Ru x ]octO y , where tet refers to the tetrahedral site and oct the octahedral one. The electrical transport property of the solid solutions exhibited semiconducting behavior and positive Seebeck coefficient in the temperature range from 298 to 1073K. The thermal conductivity increased with increasing temperature. The maximum dimensionless figure of merit of 0.024 was measured for Co2.35Ru0.65O3.86 at 973K. [Copyright &y& Elsevier]

Pressure-induced structural phase transition of spin ladder compound SrCu2O3 was investigated by synchrotron X-ray powder diffraction with a diamond anvil cell (DAC). The change was characterized by a buckling of the Cu2O3 plane in the rung direction of the ladder. The structure of the high-pressure phase was found to be essentially the same as that of CaCu2O3. Application of an external pressure of 3.4 OPa therefore affected the structure in the same manner that the chemical (internal) pressure does. [ABSTRACT FROM AUTHOR]

Abstract: Ternary nitrides, Li3XN2 (X=B, Al, Ga), were prepared at 973–1073K in N2 by solid state reaction of Li3N and XN. Among these three compounds, Li3GaN2 reacted with H2 gas at 573K and changed into a mixture of LiNH2, LiH, and GaN. The amount of hydrogen reacted was 3.4mass% to the amount of Li3GaN2, and 1.7mass% of hydrogen was released under a reduced pressure. [Copyright &y& Elsevier]