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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 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 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]

SmFeGe2O7 germanate has been synthesized by solid-state reactions from stoichiometric mixtures of starting oxides using multistage sintering in the temperature range 1273‒1473 K. The effect of temperature on the heat capacity of the compound has been studied by differential scanning calorimetry. On the basis of the dependence Cp = f(T), the thermodynamic properties of this compound have been calculated. [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]

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]

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]

Abstract—: Polycrystalline In2Ge2O7 and YInGe2O7 samples have been prepared by solid-state reactions, by sequentially firing stoichiometric mixtures of In2O3, Y2O3, and GeO2 at temperatures from 1273 to 1473 K. The molar heat capacity of the indium and yttrium indium pyrogermanates has been determined by differential scanning calorimetry in the range 320-1000 K. The experimental Cp(T) data have been used to evaluate the enthalpy increment, entropy change, and reduced Gibbs energy of In2Ge2O7 and YInGe2O7. [ABSTRACT FROM AUTHOR]

Polycrystalline HoBiGeO5 and ErBiGeO5 samples have been prepared by solid-state reactions, by firing stoichiometric mixtures of Ho2O3 (Er2O3), Bi2O3, and GeO2. The effect of temperature on the heat capacity of the synthesized compounds has been investigated by differential scanning calorimetry in the range 350-1000 K. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of bismuth holmium and bismuth erbium germanates: enthalpy increment, entropy change, and reduced Gibbs energy. [ABSTRACT FROM AUTHOR]

The Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates have been prepared by solid-state reactions in several sequential firing steps in the temperature range 1237-1473 K using stoichiometric mixtures of Dy2O3 (or Ho2O3) and GeO2. The heat capacity of the synthesized germanates has been determined as a function of temperature by differential scanning calorimetry in the range 350-1000 K. The experimentally determined Cp(T) curves of the dysprosium and holmium germanates have no anomalies and are well represented by the Maier-Kelley equation. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of the Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates: enthalpy increment H°(T)-H°(350 K), entropy change S°(T)-S°(350 K), and reduced Gibbs energy Ф°(T). [ABSTRACT FROM AUTHOR]

The Sm2Ge2O7 and Eu2Ge2O7 germanates have been prepared by solid-state reactions via multistep firing of stoichiometric mixtures of Sm2O3 (Eu2O3) and GeO2 in air at temperatures from 1273 to 1473 K. The molar heat capacity of the samarium and europium germanates has been determined by differential scanning calorimetry in the range 350-1000 K and the Cp(T) data have been used to evaluate their thermodynamic properties. [ABSTRACT FROM AUTHOR]

The Pb8La2(GeO4)4(VO4)2 and Pb8Nd2(GeO4)4(VO4)2 germanatovanadates with the apatite structure have been prepared by solid-state reactions, by sequentially firing stoichiometric mixtures of PbO, La2O3 (Nd2O3), GeO2, and V2O5 in air at temperatures of 773, 873, 973, and 1073 K. The effect of temperature on the heat capacity of the resultant polycrystalline samples has been studied by differential scanning calorimetry at temperatures from 350 to 950 K using polycrystalline samples. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of the lead lanthanum and lead neodymium germanatovanadates. [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]

Polycrystalline HoBiGeO5 and ErBiGeO5 samples have been prepared by solid-state reactions, by firing stoichiometric mixtures of Ho2O3 (Er2O3), Bi2O3, and GeO2. The effect of temperature on the heat capacity of the synthesized compounds has been investigated by differential scanning calorimetry in the range 350-1000 K. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of bismuth holmium and bismuth erbium germanates: enthalpy increment, entropy change, and reduced Gibbs energy. [ABSTRACT FROM AUTHOR]

The Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates have been prepared by solid-state reactions in several sequential firing steps in the temperature range 1237-1473 K using stoichiometric mixtures of Dy2O3 (or Ho2O3) and GeO2. The heat capacity of the synthesized germanates has been determined as a function of temperature by differential scanning calorimetry in the range 350-1000 K. The experimentally determined Cp(T) curves of the dysprosium and holmium germanates have no anomalies and are well represented by the Maier-Kelley equation. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of the Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates: enthalpy increment H°(T)-H°(350 K), entropy change S°(T)-S°(350 K), and reduced Gibbs energy Ф°(T). [ABSTRACT FROM AUTHOR]