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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]

Pb10 –xSmx(GeO4)2 +x(VO4)4 –x (x = 0.2, 0.5, 0.7, 1.0) compounds with the apatite structure have been synthesized by firing appropriate mixtures of the PbO, Sm2O3, GeO2, and V2O5 oxides in air at temperatures from 773 to 1073 K. Their crystal structure has been studied using X-ray diffraction, and their high-temperature heat capacity (350–1000 K) has been determined by differential scanning calorimetry. The data have been used to evaluate their thermodynamic properties. [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]

The RxBi2– xGeO5 (R = Sm–Yb, Y) and BiGeO5 (R1 = Y, R2 = Pr, Nd) germanates have been prepared by solid-state reactions, by sequential firing of oxide mixtures in air in the temperature range 1003–1223 K. Their heat capacity has been determined by differential scanning calorimetry. The Cp(T) data have been shown to be well represented by the classic Maier–Kelley equation in the range 350–1000 K. [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]

The Bi12TiO20, Bi4Ti3O12, and Bi2Ti4O11 bismuth titanates have been prepared by solid-state reactions, via multistep firing of stoichiometric mixtures of their constituent oxides in air at temperatures from 1003 to 1273 K (Bi12TiO20, to 1123 K). The heat capacity of polycrystalline samples of the synthesized compounds has been determined by differential scanning calorimetry in the temperature range 330–1050 K. The Cp(T) curves of Bi4Ti3O12 and Bi2Ti4O11 show peaks at temperatures of 943 and 509 K, respectively, due to ferroelectric phase transitions. The experimental data have been used to evaluate the enthalpy increment, entropy change, and reduced Gibbs energy change of the bismuth titanates. [ABSTRACT FROM AUTHOR]

The R2Ge2O7 (R = Pr–Lu, Y) rare-earth germanates have been prepared by solid-state reactions by firing stoichiometric R2O3 + GeO2 mixtures in air at temperatures in the range 1273–1473 K. The unit-cell parameters (a, c, and V) of the R2Ge2O7 (R = Tb–Lu) compounds have been shown to be linear functions of the ionic radius of the rare-earth elements. The high-temperature heat capacity of polycrystalline samples of the germanates has been determined by differential scanning calorimetry in the temperature range 350–1000 K. The variation in the specific heat of R2Ge2O7 has been shown to be correlated with the dependence of the heat capacity of rare-earth oxides on the ionic radius of the rare-earth element within each tetrad. [ABSTRACT FROM AUTHOR]

Pb10 –xLax(GeO4)2 +x(VO4)4 –x (x = 0, 1, 3) compounds with the apatite structure have been prepared by solid-state reactions via multistep firing of appropriate oxide mixtures in air in the temperature range 773–1073 K. The heat capacity of the synthesized polycrystalline samples has been determined by differential scanning calorimetry. The experimental Cp(T) data have been used to evaluate the thermodynamic properties of the lead lanthanum germanatovanadates: enthalpy increment, entropy change, and reduced Gibbs energy. [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 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]