Internal friction measurements were performed at temperatures ranging from 300 to 1100K, using frequencies ranging from 7.8 to 144kHz. It was found that a marked damping peak appeared at about 800K, when using a frequency of 40kHz. This peak was attributed to O atoms which hopped in the basal plane. The O diffusion coefficient which was deduced from the hopping relaxation time agreed well with other estimates, and indicated an activation enthalpy of 1.07eV; with a frequency-factor of 0.00018cm2/s. The diffusion coefficient began to increase rapidly at a composition of Cu3Ba2YO6.75.

J.L.Talon, M.P.Staines: Journal of Applied Physics, 1990, 68[8], 3998-4001