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Lithium sodium tetragermanate, LiNaGe4O9, has been prepared by solid-state reaction, by sequentially firing stoichiometric mixtures of Li2CO3, Na2CO3, and GeO2 starting materials in air in the temperature range 773–1073 K. Its unit-cell parameters have been determined by X-ray diffraction: a = 4.68007(3) Å, b = 9.3220(8) Å , c = 15.900(2) Å, and V = 694.113 Å (Z = 4, sp. gr. Pcca). The high-temperature heat capacity of the germanate has been determined using differential scanning calorimetry in the temperature range 320–1050 K. The experimental temperature-dependent heat capacity data, Cp(T), have been used to calculate the principal thermodynamic functions of LiNaGe4O9. [ABSTRACT FROM AUTHOR]

The RGaTi2O7 (R = Sm, Ho, Tm, Yb) substituted titanates have been prepared by solid-state reactions, by firing mixtures of the Ga2O3, TiO2, and R2O3 oxides in air at 1273 and 1573 K, and their crystal structure has been determined using X-ray diffraction. The effect of temperature (320–1000 K) on the heat capacity of the synthesized compounds has been studied by differential scanning calorimetry. The experimental Cp(T) data have been used to calculate the principal thermodynamic functions of the titanates. Using the group contribution method, we evaluated the standard enthalpy and Gibbs energy of formation of the RGaTi2O7 (R = Sm, Ho, Tm, Yb) titanates. [ABSTRACT FROM AUTHOR]

The CaY2Ge3O10 and CaY2Ge4O12 germanates have been synthesized by a standard ceramic processing route using CaCO3, Y2O3, and GeO2 as starting materials, and their crystal structure has been refined by X-ray diffraction. The high-temperature (350–1000 K) experimental heat capacity data obtained for the germanates by differential scanning calorimetry have been used to calculate their principal thermodynamic functions. [ABSTRACT FROM AUTHOR]

Copper samarium germanate CuSm2Ge2O8 have been synthesized by the ceramic method from CuO, Sm2O3, and GeO2 in air at the final calcination temperature 1273 K (200 h), and its crystal structure has been determined (space group Cm; a = 9.7592(2) Å, b = 15.2608(4) Å, c = 8.2502(2) Å, β = 148.2566(8)°, V = 646.46(3) Å3). The temperature dependence of the molar heat capacity Cp= f(T) measured in the temperature range 350–1000 K shows a maximum at Tmax = 498.5 K caused by the phase transition. Thermodynamic properties have been calculated from experimental data. [ABSTRACT FROM AUTHOR]

Pb10 –xEux(GeO4)2 +x(VO4)4 –x (x = 0.1, 0.2, 0.3) Eu-substituted lead germanatovanadates with the apatite structure have been prepared by solid-state reactions, via firing in air in the temperature range 773–1073 K, using oxides (PbO, Eu2O3, GeO2, and V2O5) as starting materials. Using X-ray diffraction, we have determined the hexagonal cell parameters (sp. gr. P63/m) of the synthesized phases and refined their crystal structure (the atomic position coordinates, isotropic thermal parameters, and principal bond lengths in their structure are presented). We have measured the luminescence spectra of the Pb10 –xEux(GeO4)2 +x(VO4)4 –x (x = 0.1, 0.2, 0.3) apatites and shown that europium concentration has little effect on the shape of the luminescence spectra. Using experimental heat capacity data obtained for polycrystalline samples by differential scanning calorimetry in the temperature range 350–1050 K, we calculated the main thermodynamic functions of the Eu-substituted lead germanatovanadates. [ABSTRACT FROM AUTHOR]

Bi4–xPrxTi3O12 (x = 0.4, 0.8, 1.2, 1.6) solid solutions have been prepared by solid-state reactions, via multistep firing of stoichiometric mixtures of their constituent oxides in air at temperatures from 1003 to 1323 K. Their crystal structure has been determined using X-ray diffraction, and their luminescence spectra have been measured at room temperature. High-temperature heat capacity of polycrystalline substituted bismuth titanate samples has been determined by differential scanning calorimetry. The Cp(T) curves of the solid solutions with x = 0.4 and 0.8 have extrema related to phase transitions. Experimental data have been used to calculate the main thermodynamic functions of the solid solutions. [ABSTRACT FROM AUTHOR]

The DyGaTi2O7 and EuGaTi2O7 titanates have been prepared by solid-state reactions in a starting mixture of Dy2O3 (Eu2O3), Ga2O3, and TiO2 via firing in air at temperatures of 1273 and 1573 K, and their crystal structure has been studied by X-ray diffraction. Their high-temperature heat capacity (350–1000 K) has been determined by differential scanning calorimetry. The Cp(T) experimental data have been used to calculate the thermodynamic functions of the titanates. [ABSTRACT FROM AUTHOR]

Single-phase LuGaTi2O7 samples have been prepared by solid-state reaction in a starting mixture of Lu2O3, Ga2O3, and TiO2 via sequential firing in air at temperatures of 1273 and 1573 K. The crystal structure of the lutetium gallium dititanate has been determined by the Rietveld method (profile analysis of X-ray diffraction patterns of polycrystalline powders): sp. gr. Pcnb; a = 9.75033(13) Å, b = 13.41425(17) Å, c = 7.29215(9) Å, V = 957.32(2) Å3, d = 6.28 g/cm3. The heat capacity of LuGaTi2O7 has been determined as a function of temperature by differential scanning calorimetry in the range 320–1000 K. The Cp(T) data thus obtained have been used to calculate the principal thermodynamic functions of the oxide compound. [ABSTRACT FROM AUTHOR]

Pb10 –xPrx(GeO4)2 +x(VO4)4– x (x = 0, 1, 2, 3) apatites have been prepared by solid-state reactions via sequential firing of appropriate oxide mixtures (PbO, Pr2O3, GeO2, and V2O5) in air in the temperature range 773–1073 K. Their unit-cell parameters have been determined as functions of temperature by high-temperature X-ray diffraction measurements, and the linear and volume expansion coefficients of Pb7Pr3(GeO4)5(VO4) have been calculated. The heat capacity of the synthesized Pb10 –xPrx(GeO4)2 +x(VO4)4– x (x = 0, 1, 2, 3) compounds with the apatite structure has been determined by differential scanning calorimetry in the temperature range 350–1050 K. The cp(T) curves of the samples with x = 1, 2, and 3 have been shown to have extrema (in particular, peaks at 701, 917, and 1018 K for the x = 3 sample) due to phase transitions. The experimental Cp(T) heat capacity data have been used to evaluate the thermodynamic functions of the synthesized apatites. [ABSTRACT FROM AUTHOR]

The europium gallium germanate EuGaGe2O7 has been prepared by solid-state reaction in air in the temperature range 1273–1473 K using a stoichiometric mixture of Eu2O3, Ga2O3, and GeO2. Its crystal structure has been determined by X-ray diffraction (sp. gr. P21/c, a = 7.1693(7) Å, b = 6.57008(6) Å, c = 12.7699(1) Å, β = 117.4522(5)°, V = 533.768(8) Å3). The heat capacity of polycrystalline samples has been determined by differential scanning calorimetry in the temperature range 350–1053 K and the experimental data have been used to calculate the thermodynamic properties (enthalpy increment, entropy change, and reduced Gibbs energy change) of EuGaGe2O7. [ABSTRACT FROM AUTHOR]

Gadolinium germanate, Gd2Ge2O7, has been prepared by solid-state reaction, via multistep firing in the temperature range 1273–1473 K, and its high-temperature heat capacity has been determined by differential scanning calorimetry. The Cp(T) data have been used to evaluate the thermodynamic functions (enthalpy increment, entropy change, and reduced Gibbs energy) of the oxide compound. [ABSTRACT FROM AUTHOR]

The Gd2Ti2O7 and Lu2Ti2O7 titanates (pyrochlore structure, sp. gr. Fd3m) have been prepared by solid-state reactions in air at temperatures from 1673 to 1773 K using the Gd2O3, Lu2O3, and TiO2 oxides as starting materials. Their high-temperature heat capacity has been determined by differential scanning calorimetry in the range 350–1000 K. The experimental heat capacity data have been used to evaluate the thermodynamic functions of gadolinium and lutetium dititanates. [ABSTRACT FROM AUTHOR]

Oxides Y0.65Pr0.35BiGeO5 and Y0.65Nd0.35BiGeO5 have been synthesized by a ceramic method. The heat capacity of fine crystalline samples has been studied in the range 350-1000 K by differential scanning calorimetry. The Cp = f(T) dependences can be described by the Maier-Kelley equation. The thermodynamic functions of these oxides—changes in enthalpy, entropy, and reduced Gibbs energy—have been calculated from the experimental data on high-temperature heat capacity. [ABSTRACT FROM AUTHOR]

ErInGe2O7 and TbInGe2O7 have been synthesized from the parent oxides by a ceramic method through the multistep annealing in air in the temperature range 1273–1473 K. The high-temperature heat capacity of these oxides has been measured by the differential scanning calorimetry method (350–1000 K). Their thermodynamic properties have been calculated from the experimental dependences Cp = f(T). [ABSTRACT FROM AUTHOR]

The heat capacity of InCuO has been determined by differential scanning calorimetry in the temperature range 364-984 K. The C( T) data have been used to evaluate the thermodynamic functions of indium cuprate: enthalpy increment H( T) - H(364 K) and entropy change S( T) − S(364 K). [ABSTRACT FROM AUTHOR]

The effect of temperature within the range 379-1026 K on the specific heat of thulium orthovanadate TmVO obtained by solid-phase synthesis was studied by differential scanning calorimetry. From the experimental dependence C = f( T), which is described by the equation C = (136.46±0.47) + (15.5±0.5) × 10 T - (17.5±0.6) × 10T, the thermodynamic functions of the oxide compound were calculated. [ABSTRACT FROM AUTHOR]

The europium gallium germanate EuGaGe2O7 has been prepared by solid-state reaction in air in the temperature range 1273–1473 K using a stoichiometric mixture of Eu2O3, Ga2O3, and GeO2. Its crystal structure has been determined by X-ray diffraction (sp. gr. P21/c, a = 7.1693(7) Å, b = 6.57008(6) Å, c = 12.7699(1) Å, β = 117.4522(5)°, V = 533.768(8) Å3). The heat capacity of polycrystalline samples has been determined by differential scanning calorimetry in the temperature range 350–1053 K and the experimental data have been used to calculate the thermodynamic properties (enthalpy increment, entropy change, and reduced Gibbs energy change) of EuGaGe2O7. [ABSTRACT FROM AUTHOR]