Effect of Cu-substitution on the conductivity of Ag-rich AgI–CuI solid solutions

Abstract

The ionic conductivity of the silver rich solid solutions Ag 1− x Cu x I (0< x<0.25) was measured using complex impedance spectroscopy over the frequency range 100 Hz–15 MHz and in the temperature range 25–250 °C. As observed in undoped AgI, two conducting regions (above and below T c) are found in these solid solutions also. Despite the large size difference in the ionic radii of Ag + and Cu + ions, the bigger sized Ag + ion dominates the overall conductivity of the system. Arrhenius plots of the dc conductivity demonstrates clearly the enhanced defect concentration and grain boundary effects in the low temperature phase as well as the smallness of the observed activation energy along with the softening of the AgI lattice in the high temperature phase. The pertinent effect of Cu doping in AgI is discussed in terms of the recent experimental and theoretical facts. A plausible conduction mechanism is being worked out.