N. A. Galiakhmetova

High-temperature heat capacity of YBiGeO 5 and GdBiGeO 5 in the range 373–1000 K

The oxide YBiGeO5 and GdBiGeO5 compounds have been synthesized by solid-phase synthesis. The high-temperature heat capacity has been measured using differential scanning calorimetry in the range 373–1000 K. The results were used to calculate the thermodynamic properties (the change in the enthalpy and entropy).

Heat capacity of GdBiGeO5 in the temperature range 373–1000 K

Ternary oxide GdBiGeO5 was synthesized by a ceramic method. The heat capacity of crystalline gadolinium bismuth germanate as a function of temperature in the range 373–1000 K has been studied by differential scanning calorimetry. It has been demonstrated that the temperature dependence of the heat capacity can be described by the classical Maier–Kelley equation. From the experimental CP = f(T) data, the thermodynamic functions (the change in enthalpy and entropy) of ternary oxide GdBiGeO5 have been calculated.

High-temperature specific heat of Bi 2 GeO 5 and SmBiGeO 5 compounds

The SmBiGeO5 compound is synthesized from Sm2O3, Bi2O3, and GeO2 by solid-state synthesis with subsequent annealing at 1003, 1073, 1123, 1143, 1173, and 1223 K. The metastable Bi2GeO5 compound is prepared from melt. Temperature dependences of specific heat of Bi2GeO5 (350–1000 K) and SmBiGeO5 (370–1000 K) are measured by differential scanning calorimetry. Basing on the experimental dependences CP = f(T), the thermodynamic functions of the oxide compounds are calculated.

High-temperature heat capacity of oxides of the CuO–V2O5 system

CuV2O6 and Cu2V2O7 compounds have been produced from initial components CuO and V2O5 by solid-phase synthesis. The high-temperature heat capacity of the oxide compounds has been measured using differential scanning calorimetry. The thermodynamic properties (the enthalpy change, the entropy change, and the reduced Gibbs energy) have been calculated using experimental dependences CP = f(T). It is found that there is a correlation between the specific heat capacity and the composition of oxides of the CuO–V2O5 system.

High-temperature heat capacity of the oxide compounds in the Bi2O3–V2O5 system

The compounds BiVO4, Bi4V2O11, and Bi12V2O23 have been prepared by solid-state synthesis using stoichiometric mixtures of Bi2O3 and V2O5. The effect of temperature on the heat capacity of the synthesized bismuth vanadates has been studied by differential scanning calorimetry in the range 350–950 K. The Cp(T) curves have extrema at 531.7 K for BiVO4 and at 725.2 and 852.8 K for Bi4V2O11, which are due to polymorphic transformations of these compounds.

High-Temperature Specific Heat of the TmBiGeO 5 and YbBiGeO 5 Compounds

The TmBiGeO5 and YbBiGeO5 compounds have been synthesized from Tm2O3 (Yb2O3), Bi2O3, and GeO2 oxides by the solid-state synthesis with successive burning at 1003, 1073, 1123, 1143, 1173, and 1223 K. High-temperature specific heat of the oxide compounds has been measured by differential scanning calorimetry. Basing on the experimental dependences Cp = f(T), the thermodynamic properties of the oxide compounds, i.e., the enthalpy and entropy variations, have been calculated.

High-Temperature Heat Capacity of Zn 2 V 2 O 7 –Cu 2 V 2 O 7 Solid Solutions

Differential scanning calorimetry has been used to study the influence of temperature on the heat capacity of synthesized vanadates Zn2V2O7, (Cu0.56Zn1.44)V2O7, and (Cu1.0Zn1.0)V2O7. It is found that dependences Cp = f(T) have extremes. The thermodynamic properties of Zn2V2O7 have been determined.

Synthesis and High-Temperature Heat Capacity of Pb 8 La 2 (GeO 4 ) 4 (VO 4 ) 2 and Pb 8 Nd 2 (GeO 4 ) 4 (VO 4 ) 2 with the Apatite Structure

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.

High-temperature heat capacity of CdO–V2O5 oxides

Vanadates Cd2V2O7 and CdV2O6 have been prepared from CdO и V2O5 by three-phase synthesis with subsequent burning at 823–1073 K and 823–853 K, respectively. The molar heat capacity of these oxide compounds has been measured by differential scanning calorimetry. The enthalpy change, the entropy change, and the reduced Gibbs energy are calculated using the experimental dependences Cp = f(T). It is shown that there is a correlation between the specific heat capacity and the composition of CdO–V2O5 oxide system.

High-temperature heat capacity and thermodynamic properties of TbBiGeO5 and DyBiGeO5

Polycrystalline TbBiGeO5 and DyBiGeO5 samples have been prepared by solid-state reactions, by firing stoichiometric mixtures of Tb2O3 (Dy2O3), Bi2O3, and GeO2 in air at 1003, 1073, 1123, 1143, 1173, and 1223 K. The molar heat capacity of the bismuth terbium and bismuth dysprosium germanates has been determined by differential scanning calorimetry. The experimental Cp(T) data obtained in the range 350–1000 K have been used to evaluate the thermodynamic functions of the synthesized oxide compounds: enthalpy increment, entropy change, and reduced Gibbs energy.