High-temperature heat capacity and thermodynamic properties of TbBiGeO and DyBiGeO.

Polycrystalline TbBiGeO and DyBiGeO samples have been prepared by solid-state reactions, by firing stoichiometric mixtures of TbO (DyO), BiO, and GeO 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 C ( 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. [ABSTRACT FROM AUTHOR]