Semiconductors

Synthesis, crystal structure and high-temperature heat capacity of substituted apatites Pb$_9R$(GeO$_4$)$_3$(VO$_4$)$_3$ ($R$ = Tb, Dy, Ho)

L. T. Denisova^a, M. S. Molokeev^ab, E. O. Golubeva^a, N. V. Belousova^a, V. M. Denisov<sup>a

a</sup> Siberian Federal University, Krasnoyarsk
^b L. V. Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, Krasnoyarsk, Russia

Abstract: Pb$_9R$(GeO$_4$)$_3$(VO$_4$)$_3$ ($R$ = Tb, Dy, Ho) apatites were obtained by solid-phase synthesis from the initial oxides of PbO, Tb$_2$O$_3$ (Dy$_2$O$_3$, Ho$_2$O$_3$), GeO$_2$ and V$_2$O$_5$ 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.

Received: 11.04.2022
Revised: 11.04.2022
Accepted: 19.04.2022

DOI: 10.21883/FTT.2022.11.53315.353

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