Transport Studies of Copper Iodide

Abstract

Measurements of thermoelectric power (\varTheta) and electrical conductivity (σ) of copper iodide, which becomes superionic conductor above 642 K, have been reported both in α and β phases. A sharp change in magnitude of thermoelectric power has been observed at 642 K corresponding to β to α phase transition. The result may be expressed by the relations β-CuI, \varTheta= -(0.20±0.02)(10^3/T)+(0.11\mp0.02)_mV/K300–520 K α-CuI, \varTheta= -(0.098±0.005)(10^3/K)+(0.417 \mp0.005)_mV/K642–850 K. From conductivity data the activation energy ( E a ) for conduction in α and β phases of CuI is found to be 0.13 and 0.368 eV respectively and heat of transport ( q Cu +) of cationically disordered Cu + ion in α-phase and interstitial Cu + ion in β-phase have been found to be 0.098 and (0.20- h /2) eV respectively; h being the heat of formation of Frenckel defect pair in β-phase. It has been shown that the result on α-CuI supports the extended lattice gas model of superionic conductors.