Effect of the Particle Habit on the Heat Capacity and Thermodynamic Functions of EuPO4 in the Range 7–1600 K

Abstract

The effect of particle morphology on the thermodynamic properties of europium orthophosphate was studied. A EuPO4 sample free of adsorbed impurities and water having well-edged whisker particles up to 6 µm long and 0.15–0.30 µm in diameter was hydrothermally prepared. The heat capacity of EuPO4 whiskers was studied in the range 7.12–1319.3 K. Thermodynamic functions were calculated over the whole temperature range. The data gained were used to determine the effect of the particle habit on the ratio between the enthalpy and entropy factors and their contributions to the free energy of europium orthophosphate. The anomalous heat capacity term of EuPO4 whiskers in the range 0–900 K was evaluated.