IONIC-CONDUCTION IN SILVER PHOSPHATE-GLASSES DOPED WITH SILVER SULFIDE

The dielectric properties of (Ag2S)(x)(AgPO3)(1-x) and AgPO3 ionic gla sses have been investigated at low frequencies (10 Hz - 10 MHz) by com plex impedance measurements in the temperature range between 20 and 33 0 K and at microwave frequencies (8.2-18 GHz) using a waveguide transm ission line and also a cavity resonator at 9 GHz from 77 to 300 K. Ana lysis on the basis of the jump relaxation model has shown that transla tional and reorientational hopping motions of mobile Ag+ ions are resp onsible for the observed frequency-dependent ac conductivity. The temp erature dependence of the ac conductivity at fixed frequencies can be fitted using three relaxation processes with characteristic activation energies which differ from each other by an order of magnitude and ar e closely similar to those obtained from previous ultrasonic attenuati on studies on the same glasses. The highest energy (about 0.4 eV) has been associated with the translational hopping motion, responsible for the long-range ionic diffusion through the glasses in the low-frequen cy limit. The smallest activation energy (about 10 meV) has been ascri bed to the topological disorder characteristic of glassy materials and probably corresponds to ion hopping between nearly energetically equi valent available sites. The intermediate energy values (0.05 - 0.1 eV) , which depend on the concentration of the modifier, are likely to cha racterize different reorientational motion and/or different jump lengt hs.