Thermodynamic investigations of Sr- and Mg-doped lanthanum gallate by Knudsen effusion mass spectrometry and defect chemical analysis

Abstract

The vaporization of the La_1−xSr_xGa_1−yMg_yO_3−(x+y)/2 perovskite phases was investigated by the use of Knudsen effusion mass spectrometry in the temperature range of 1608–1901 K. The partial pressures of the gaseous species O₂, Mg, Sr, SrO, Ga, GaO, Ga₂O and LaO were determined over the samples investigated. The equilibrium partial pressures were used for the calculation of thermodynamic activities of Ga₂O₃ (1700 K), MgO (1800 K) and SrO (1800 K) in the perovskite phase at the temperatures given in parentheses. The results are compared with the thermodynamic data of LaGaO₃(s) without additives. The influence of the Mg concentration on the thermodynamic activity of Ga₂O₃ was carefully studied and modeled by a defect chemical analysis.