Vaporization and thermodynamics of La1-xCaxCrO3-delta investigated by Knudsen effusion mass spectrometry

摘要

Vaporization of the La1-xCaxCrO3-delta perovskite phase, x = 0.047-0.21, was investigated by the use of Knudsen effusion mass spectrometry in the temperature range of 1950-2050 K. Ion intensities were assigned to the neutral precursors by the isothermal evaporation method in addition to literature data. The partial pressures of Cr(g), CrO(g), CrO,(g), CaO(g), and LaO(g) were determined for all the samples investigated. The partial pressure of O-2(g) was evaluated from the gaseous equilibria. The experimental data were interpreted using the phase equilibria in the CaO-Cr2O3-La2O3 system under low oxygen pressure we previously studied. The ion intensities were used to calculate the thermodynamic activities of the system components at 2000 K. The Gibbs energy of formation of La0.79Ca0.21CrO3 at 2000 K was estimated from the thermodynamic activities as -81.5 kJ mol(-1). The results were compared with thermodynamic data of the undoped LaCrO3(s). Implications of the present data for the potential use of the material in SOFC technology were discussed as well. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 24]