Third law entropy of Barium molybdate

Abstract

The isobaric heat capacities, C°p,m, for BaMoO4 at 2-300 K were measured by the relaxation method. The third law entropy, S°m, was determined via the Debye-Einstein function into which the Debye temperature, ΘD, as physico-chemical constant and a thermal expansion term were incorporated. ΘD was determined from C°p,m at very low temperatures. The obtained thermodynamic properties were: S°m (BaMoO4(cr), 298.15 K)/JK-1 mol-1 = 152.69 ± 1.53; ΘD(BaMoO4(cr))/K = 295 ± 3. The phase stability of BaMoO4 was discussed on the basis of its standard Gibbs energy of formation, ΔfG°m. It was derived by combining S°m determined in this study with the reference data of the standard enthalpy of formation, ΔfH°m. The thermodynamic properties obtained in the present study can be used for evaluating the hierarchy for formation of the yellow phase related-substances in nuclear waste glasses.