A low-frequency internal friction peak which was due to O diffusion in basal CuO planes was observed in the orthorhombic material by performing forced torsional vibration experiments at temperatures ranging from 385 to 471K (0.0001 to 30Hz). An apparent activation energy of 0.98eV was measured. This corresponded to an activation energy for O diffusion of 0.68eV; assuming a KWW relaxation function.

J.Woirgard, P.Gadaud, A.Rivière, B.Kaya: Materials Science Forum, 1993, 119-121, 719-24