IMPEDANCE AND MODULUS SPECTROSCOPIC STUDIES ON (CUL)(100-X)-(AG2SO4)(X) -LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-60) MIXED SYSTEM

The frequency-dependent conductivity, sigma(omega) measurements on (Cu l)(100-x)-(Ag2SO4)(x) (0 less than or equal to x less than or equal to 60) mixed system in the frequency range 1 Hz-65.5 kHz and over the te mperature range 293-403 K have been carried out. These studies have il lustrated similarities in the behaviour of the present system and the other fast ionic solid systems which are generally found to obey the J onscher's universal power law, sigma(a.c.)(omega) = sigma(0) + A omega (n), where sigma(a.c.)(omega) is the conductivity at frequency omega, sigma(0) is the limiting zero frequency conductivity or d.c. conductiv ity and A and n are fitting parameters. The value of n decreases with increasing temperature and A and sigma(0) increase with temperature (n is a temperature-dependent frequency exponent, A is a frequency-indep endent and temperature-dependent parameter). These results appear to s uggest a mechanism of fast ion conduction due to the presence of well- defined pathways. The strong low-frequency dispersion observed in the case of high conductivity compositions is attributed to the electrode polarization effects. The observed impedance and modulus spectra in co rrelation with the Arrhenius plots obtained at different frequencies h ave clearly indicated the frequency dispersion of conduction due to ma ny-body effects and the formation of a large capacitance associated wi th the electrodes. Thus, the present analysis has suggested a non-Deby e type of relaxation process arising due to many-body effects and a di stribution of relaxation times, which is a temperature-independent phe nomenon exhibited by the heterogeneous electrical structure of the mix ed system.