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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]

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]

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]