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Pb9R(GeO4)3(VO4)3 (R=Tb, Dy, Ho) apatites were obtained by solid-phase synthesis from the initial oxides of PbO, Tb2O3 (Dy2O3, Ho2O3), GeO2 and V2O5 by sequential annealing (at a temperature of 773-1073 K) in an air atmosphere. Their crystal structure has been determined by X-ray diffraction analysis. The high-temperature heat capacity was measured by differential scanning calorimetry. Based on the experimental dependence of the heat capacity on the temperature, the thermodynamic properties are calculated. Keywords: apatites, solid-phase synthesis, crystal structure, heat capacity, thermodynamic properties. Keywords: apatites, solid-phase synthesis, crystal structure, heat capacity, thermodynamic properties.

Apatite Pb3Bi2(GeO_4)3 was obtained by the solid-phase method from the initial oxides of PbO, Bi2O3 and GeO2 by sequential firing in air at temperatures of 773-1003 K. Its crystal structure has been refined by X-ray diffraction. The high-temperature heat capacity (350-1000 K) of this compound was measured by differential scanning calorimetry. Based on these data, the main thermodynamic functions are calculated. Keywords: apatite bismuth-lead germanate, solid-phase synthesis, high-temperature heat capacity, thermodynamic properties Keywords: apatite bismuth-lead germanate, solid-phase synthesis, high-temperature heat capacity, thermodynamic properties.