Coefficients for O diffusion were calculated by using the pair approximation in the path probability method. The results showed that O diffusion in this compound depended significantly upon the O density and upon the degree of long-range order. It was found that the O diffusion rate in the tetragonal phase was faster than that in the orthorhombic phase; with activation energies for diffusion of 0.8 and 1.2eV, respectively. The rate changed abruptly when phase transformation took place.

J.S.Choi, M.Sarikaya, I.A.Aksay, R.Kikuchi: Physical Review B, 1990, 42[7], 4244-54