Synthesis, Crystal Structure, and High-Temperature Heat Capacity of Pb10 –xSmx(GeO4)2 +x(VO4)4 –x (x = 0.2, 0.5, 0.7, 1.0) Apatites from 350 to 1000 K

https://doi.org/10.1134/S0020168522070081

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.