DIELECTRIC-PROPERTIES AND GLASSY BEHAVIOR IN THE SOLID-SOLUTION CERAMICS PB(ZN1 3NB2/3)O-3-PBTIO3-BATIO3/

The dielectric behaviour of the solid-solution ceramics Lax/2Kx/2)(Zn1 /3Nb2/3)O-3-0.8PbTiO(3)-0.05BaTiO(3) with x = 0, 0.04, 0.08 and 0.12, was measured and analysed ill a broad temperature range and at frequen cies from 100 Hz to 100 kHz. It was found that the relation between th e temperature and the dielectric constant can be well expressed by an exponential function exp(alpha - betaT) at temperatures much higher t han the temperature T-m of the dielectric constant maximum and that th ere is a super-exponential relation exp[alpha(1) + (T/beta(1))(1+delta )] at temperatures much lower than T-m. This indicates that the glassy behaviour of the materials is different from that of general glasses. The freezing temperature of the polar regions in these materials is d istributed over a broad temperature range, which results in dielectric dispersion of the materials at low temperatures. This demonstrates th at both the distribution of the freezing temperatures and the process by which the polar regions are produced are associated with the degree of dielectric relaxation of the materials. Therefore, at least two fa ctors, such as delta and beta, are needed to describe the dielectric r elaxation of the materials completely. The relation between the logari thm of the frequency and the dielectric constant at low temperatures c an be expressed as a linear function for these materials. The frequenc y dependence of T-m for the materials is analysed using the Vogel-Fulc her relationship omega = omega(0) exp[-T-0/(T-m - T-f)] and a new rela tionship omega = omega(0) exp[-(T-0/T-m)(p)]. We confirm that the new fit is much better than the Vogel-Fulcher fit.