The dissolution enthalpy at 298.15 K of intermediate compounds in LnBr3-MBr systems: CALPHAD reassessment of thermodynamics of LnBr3-MBr systems (Ln = Ce, Pr, M = K-Cs)

Abstract

The dissolution enthalpies of intermediate compounds in LnBr3-MBr (Ln = Ce, Pr, M = K-Cs) systems were measured at 298.15 K using the Calvet calorimeter. The formation enthalpies of K2CeBr5, Rb2CeBr5, Rb3CeBr6, RbCe2Br7, Cs3CeBr6, CsCe2Br7, K2PrBr5, Rb2PrBr5, RbPr2Br7, Cs3PrBr6, and CsPr2Br7 were calculated from the enthalpies of dissolution of the corresponding system components. The phase diagrams of LnBr3-MBr systems were reassessed using the CALPHAD method by applying a uniform Associate Solution Model of the liquid phase. The stability of the compounds resulting from CALPHAD modelling was analysed. Enthalpies of the formation of compounds values obtained by solution calorimetry were compared with values obtained by extrapolating CALPHAD results.