Enthalpies of formation of LaBO3 perovskites (B = Al, Ga, Sc, and In)

摘要

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 LaAlO3 and LaGaO3 are -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 LaScO3 and LaInO3 from 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. [References: 39]