RECENT PROGRESS IN THE AREA OF NMR CHARACTERIZATION OF IONIC TRANSPORT AND RELAXATION IN GLASSES

Results of temperature and frequency dependence of nuclear spin relaxa tion (NSR) are presented for different inorganic glasses between about 1 K and the glass transition temperature. Below about 200 K the data can be interpreted consistently in the framework of thermally activate d low-frequency excitations (LFEs) of disorder modes intrinsic to the glassy state. The modes are modelled by asymmetric double-well potenti al (ADWP) configurations with a suitable density of states of the barr ier height and asymmetry. Varying the nuclear probe allows the detecti on of different disorder modes. Above 200 K, NSR is dominated by diffu sive ionic jumps resulting in an asymmetric NSR rate maximum. Evaluati on of the data is shown to agree best with results of Monte Carlo (MC) simulations of the hopping process as performed by the Bunde and Diet erich group.