Elastic After-Effect Due to Oxygen Relaxation in Yba 2 Cu 3 O 7−δ Above T c

Isothermal elastic after-effect measurements to obtain relaxation times for the stress-induced motion of oxygen in YBa 2 Cu 3 O 7−δ have been made from 50 ° C to 110 ° C. These results extend our previous internal friction measurements of the same oxygen relaxation to lower temperatures. The combined results, which cover nine orders of magnitude in relaxation time, show a classical Arrhenius temperature dependence, activation energy Q−1.13±0.01 eV and attempt frequency τ 0 −1.6×10 −13 s (log τ 0 −.12.79±0.13). The mechanism of the relaxation is considered to be stress-induced ordering of oxygen atoms on theCuO basal plane. Diffusivities obtained from these results are compared with those from tracer diffusion of oxygen.