Polarization Processes in Silver Iodide Films Doped with Copper

Abstract

Using dielectric spectroscopy (DS), this study investigated the characteristics of polarization processes in copper-doped nanocrystalline silver iodide films in the region of the thermal superionic phase transition. It was found that doping with copper (5 vol %) leads to a decrease in the resonance frequency of the DS features, accompanied by an increase in the amplitude of the features in the frequency dependences of the imaginary (ε") and real (ε') components of the complex dielectric permittivity. A power-law frequency dependence of the electrical conductivity σ was observed, and the exponent s of this dependence was shown to undergo an abrupt change at the superionic phase transition temperature T_c = 433 K. The temperature dependence of the exponent s(T) was found to correspond to two charge-transport mechanisms governing electrical conductivity: thermally activated hopping conduction at T < T_c and quantum-mechanical tunneling at T > T_c. The relaxation and energy parameters of charge-transport processes in the AgI:Cu film system were calculated, making it possible to determine a non-Debye mechanism of dielectric relaxation in the AgI:Cu system.