DIELECTRIC BEHAVIOR OF ND IONS IN THE LEAD BERATE GLASS

Accurate measurements of the relaxation in the time domain show that t he low frequency relaxation processes in glasses are well described by the Williams-Watts (WW) relation. Measurements of the complex permitt ivity in the frequency domain have been often claimed, on the other ha nd, to satisfy the Cole-Davidson (CD) relation, epsilon() = epsilon(i nfinity) + [(epsilon(0) - epsilon(infinity))/(1 + j pi tau)(alpha)], 0 < alpha. In order to check with what accuracy the systems whose time domain behaviour is given by WW relation also satisfy the CD equation in the frequency domain, frequency measurements of the glasses in the frequency region 1 Hz-10 GHz are taken using different techniques. Abs orption was observed in two different frequency regions and they are w ell described by the two relations. The temperature dependence of rela xation time parameters was also studied in order to characterize the p hysics of the relaxation process. The dependence of the parameters on the concentration of Nd sheds some light on the state of aggregation o f the Nd ions in the glass.