Thermodynamic and Thermochemical Characteristics of Holmium Silicides

Abstract

The Gibbs free energy and enthalpy and entropy of formation of holmium silicides HoSi_2–a(HoSi_1,82), HoSi_2–b(HoSi_1,67), Ho₃Si₄, HoSi, HoSi_1–x (HoSi_0,98), Ho₅Si₄ and Ho₅Si₃ are determined by e.m.f. method. The heat capacity and enthalpy of HoSi_1,67 in the temperature range 55–2007 K are measured by the methods of adiabatic and drop calorimetry. The enthalpy and entropy of α → β polymorphic transformation and melting of HoSi_1,67 are established. Temperature dependencies of heat capacity and enthalpy and entropy of melting for HoSi and Ho₅Si₃ are evaluated based on the behavior of heat capacity and enthalpy of melting for mono- and lower silicides along the lanthanide row.