Solid‐State Reaction Kinetics of LaCrO3 from the Oxides and Determination of La3 + Diffusion Coefficient

The parabolic rate constant for the solid‐state reaction of was measured at temperatures between 1483 and 1688 K in air and at 1695 K in oxygen pressures between 2.1 × 10 4 and . According to Wagner's theory, the diffusion coefficient of in was evaluated using the parabolic rate constant and the standard Gibbs energy change of the reaction. The oxygen pressure dependence of the diffusion coefficient is given by where is the activity of and is the oxygen pressure. The temperature dependence of the diffusion coefficient of lanthanum ion in is given by (at higher , e.g., at 1695 K).