Dysprosium orthotantalate ceramics: Thermal expansion and heat capacity

Abstract

Monoclinic dysprosium orthotantalate ceramics were synthesised by reverse co-precipitation followed by annealing at 1773 K and characterized by X-ray powder diffraction, scanning electron microscopy and chemical analysis. High-temperature X-ray diffraction was used to study change in the lattice parameters in the temperature range of 298–1273 K, and the volume expansion of M-DyTaO4 ceramics was calculated. The molar heat capacity of M-DyTaO4 was measured by adiabatic (9–346 K) and differential scanning (316–1336 K) calorimetries. The temperature dependences of entropy, enthalpy change and reduced Gibbs energy of M-DyTaO4 in the range of 0–1273 K were calculated based on smoothed heat capacity values, without taking into account the contribution of phase transformations occurring below 9 K. The general shape of the anomalous Schottky contribution to the molar heat capacity was determined.