The appearance of 2 distinct activation energies (at high and low temperatures), an anomalously high attempt frequency, and a stretched-exponential time correlation function at low temperatures, for O-ion diffusion in yttria-stabilized material, were shown to be quantitatively consistent with the predictions of the coupling model. The anomalies, which occurred in conductivity relaxation and quasi-elastic light-scattering data, were attributed to interactions between diffusing O ions.

K.L.Ngai: Philosophical Magazine B, 1998, 77[1], 187-95