Thermodynamic properties of cerium molybdate

Abstract

Abstract Ce 2 (MoO 4 ) 3 is a harmful phase formed in waste glasses from nuclear fuel. To determine the third-law entropy of Ce 2 (MoO 4 ) 3 , the isobaric heat capacities, $C_{p,m}^^\circ $ , were measured with a relaxation-method instrument at 2–300 K. The standard entropy, $\Delta _0^TS_{\rm{m}}^^\circ $ , at 298.15 K was determined with fitting functions including the Debye–Einstein formula including electronic and spin-wave terms. The Néel temperature, T N , was estimated by extrapolation from the magnetic term in this fitting function. The phase stability of Ce 2 (MoO 4 ) 3 is discussed in terms of its standard Gibbs energy of formation, ${\Delta _f}G_{\rm{m}}^^\circ $ , which was derived by combining the values for $S_m^^\circ $ determined in this study with reference data for the standard enthalpy of formation, ${\Delta _f}H_{\rm{m}}^^\circ $ .