ION DYNAMICS IN SUPERIONIC CHALCOGENIDE GLASSES STUDIED IN LARGE FREQUENCY AND TEMPERATURE RANGES

Electrical conductivity measurements on silver thiogermanate glasses h ave been performed in extended temperature (20-600 K) and frequency (1 0 Hz-60 GHz) ranges. The data indicate the presence of three conductiv ity regimes: the d.c. regime with a deviation from Arrhenius law below the glass transition temperature, a dispersive region where sigma(ome ga) = A omega(s1) (where s(1) approximate to 0.5 and A is thermally ac tivated with an activation energy E-1 approximate to(1-s)E-d.c.) and a third regime where sigma(omega) = B omega(s2). At T<100 K the third r egime can be accounted for by an asymmetric double well potential mode l. The third regime at high frequency (GHz range) and high temperature (>150 K) shows clearly a superlinear frequency dependence. Additional measurements are needed to clearly identify the temperature dependenc e of conductivity in this region.