Recent advances in the study of fast ionically conducting glasses using nuclear magnetic resonance techniques

Abstract

Recently, Nuclear Magnetic Resonance (NMR) techniques have been applied to ionically conducting glasses with the hopes of providing better insights into the microscopic processes involved. The temperature dependent hopping of mobile cations and anions in glass result in temperature dependent effects to be seen in the NMR spectra of these “Fast Ion Conducting” glasses. We have critically reviewed progress in this field to date by examining both the theoretical background of the area and by summarizing a large number of experimental studies. One of the ubiquitous observations when examining these fast ion conducting glasses using NMR, is that the ionic motion induced spin lattice relaxation rate, 1 T 1 , exhibits a temperature dependence much less than that of the ionic conductivity. This discrepancy has been a source of much confusion in this area. We believe we provide a much needed resolution to this problem by noting that most NMR measurements are made in the MHz frequency range and for nearly all glasses this frequency range falls in a region where the ionic conductivity shows a frequency dependence and hence a temperature dependence less than that exhibited by the d.c. or frequency independent conductivity. We show that all the controversy surrounding the smaller 1 T 1 relaxation rate activation energies can therefore be eliminated by examining the full temperature and frequency dependencies of the ionic conductivity.