[en] Thermal properties of ErF₃ at high temperatures, liquid state inclusively, melting-crystallization and solid-state transition ranges were studied by the method of samples examining with a narrow gamma beam. The density and volumetric factor of liquid erbium fluoride thermal expansion at he melting point amount to 6092±30 kg/m³ and (15.1±0.5)x10^-5 K. Relative differences in density during melting and polymorphous transformation are equal to 0.75±0.1 and 16.9±1.3% respectively. The data obtained as a result of the study and literature data permit ascertaining the regularities in the change of thermal properties in the series of heavy rare earth fluorides (ErF₃-LuF₃)