Heterogeneous and Homogeneous Diffusivity in an Ion-Conducting Glass

Abstract

The nature of ion diffusivity in the vitreous conductor 2Ca(NO3)2̇3KNO3 (CKN) was studied by nonresonant dielectric hole burning. Spectral holes in the electric field relaxation are probed subsequent to a high electric sinusoidal burn field. For sufficiently high pump frequencies we are able to induce spectrally selective modifications in the relaxation of the electric modulus, indicating that ionic diffusivity is a spatially varying quantity in glassy CKN. Homogeneous behavior occurs in the regime of low pump frequencies, in which the resistivity approaches its steady state value. Thus, longer-ranged ionic motions lead to a spatial averaging over the heterogeneity of local ion diffusivities.