Dependence of activation energy and pre-exponential factor on audio frequency in glassy Se80-xTe20Snx alloys

In the present paper, we have studied the temperature and frequency dependence behaviours of ac conductivity in glassy system Se80-xTe20Snx (x = 0,2,4, and 6). All the measurements have been done in the frequency range (1-500 KHz) and in the temperature range from room temperature to glass transition temperature T-g. We have found that activation energy and pre-exponential factor both vary with audio frequency according to Meyer-Neldel's relation (MNR). We have investigated MNR by two different approaches. In first approach, the temperature dependence of ac conductivity is studied at four different audio frequencies without changing the composition of the glassy system. In the second approach, the composition itself varies at a particular audio frequency. The results are explained in terms of compensation effect in relaxation time and the multi-excitation character of the processes suggested by Yelon and Movaghar responsible for MNR in chalcogenide glasses. (c) 2010 Elsevier B.V. All rights reserved.