The diffusion coefficient of O in this orthorhombic phase was deduced from internal friction data. The diffusivity could be described by:

D (cm2/s) = 0.000183 exp[-1.23(eV)/kT]

at temperatures ranging from 400 to 550C. The results showed that the O diffusion rate in this phase was very low.

X.M.Xie, T.G.Chen, J.Huang: Physica Status Solidi A, 1988, 110[2], 415-9