Thermodynamic properties of cerium, neodymium and gadolinium sesquisulfides in wide range of temperature

Enthalpy and heat capacity of γ-modifications of cerium, neodymium and gadolinium sesquisulphides have been first investigated by the method of mixing in the range of 400-2200 K. Temperature dependences of the basic thermodynamic functions of these compounds have been obtained. An intensive increase of enthalpy in the investigated sulphides at the temperature above 1800 K is found and melting temperature of γ-Ce2S3 is determined. It is established that heat capacity of the cerium subgroup REM sesquisulphides may be represented as a sum of complete lanthanum sesquisulphide heat capacity and contributions to heat capacity by Schottky for isostructural sulphides formed by other rare-earth elements