High-temperature specific heat of the TmBiGeO$_{5}$ and YbBiGeO$_{5}$ compounds

The TmBiGeO$_{5}$ and YbBiGeO$_{5}$ compounds have been synthesized from Tm$_{2}$O$_{3}$ (Yb$_{2}$O$_{3}$), Bi$_{2}$O$_{3}$, and GeO$_{2}$ 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 $C_p = f (T)$, the thermodynamic properties of the oxide compounds, i.e., the enthalpy and entropy variations, have been calculated.