PHYSICAL ORIGINS OF THE OMEGA(1.0)-DEPENDENT AND THE OMEGA(Q)-DEPENDENT (Q-APPROXIMATE-TO-1.3) CONTRIBUTIONS TO THE CONDUCTIVITY RELAXATIONOF GLASSY IONIC CONDUCTORS

Contributions with the omega(1.0)-dependence and also the omega(q)-dep endence (q approximate to 1.3) to the ac conductivity in glassy ionic conductors are ubiquitous and have properties that differ from the ion ic diffusion contribution. These different properties suggest that the omega(1.0)-dependence contribution originates from the vibrational pa rt of the ion motion which gives rise to a time-independent mean squar e displacement related to the Debye-Waller factor. The omega(q)-depend ent contribution to the ac conductivity is related to the omega(q-1)-d ependent susceptibility on the low frequency side of the Boson peak wh ich is observed experimentally by neutron scattering and Raman scatter ing in glasses. With the ionic diffusion contribution already being we ll-described by the coupling model, this work proposes that the physic al origins of the various major contributions to the conductivity rela xation of glassy ionic conductors are now at hand. (C) 1997 Elsevier S cience B.V.