Enthalpies of formation of LaBO₃perovskites (B = Al, Ga, Sc, and In)

Enthalpies of formation from constituent oxides and elements at 298 K were determined by high-temperature oxide melt solution calorimetry for a group of technologically important perovskites LaBO₃(B = La, Ga, Sc, and In). Enthalpies of formation from oxides of LaAlO₃and LaGaO₃are −69.61 ± 3.23 kJ/mol and −52.39 ± 1.99 kJ/mol, respectively. The data were consistent with literature values obtained using other methods. The enthalpies of formation of LaScO₃and LaInO₃from oxides were reported for the first time as −38.64 ± 2.30 kJ/mol and −23.99 ± 2.31 kJ/mol, respectively. As seen for other perovskites, as the tolerance factor deviates more from unity (in the order Al, Ga, Sc, In), the enthalpy of formation from oxides becomes less exothermic, indicating a less stable structure with respect to the constituent oxides.