Formation enthalpies and heat capacities of rear earth titanates: RE2TiO5 (RE=La, Nd and Gd)

The formation enthalpies and heat capacities of orthorhombic rare earth titanates, RE2TiO5 (RE=La, Nd and Gd), have been studied by high temperature differential scanning calorimetry (300–1473 K) and oxide-melt solution calorimetry. The RE2TiO5 samples are stable in enthalpy with respect to their oxides and the pyrochlore RE2Ti2O7 phase. The general trend that has been demonstrated in other RE-ternary systems; decreasing thermodynamic stability with decreasing RA/RB was found to be valid for the RE2TiO5, and their enthalpies of formation from oxides become more negative with increasing RE3+ ionic radius.