RELAXORS AS SUPERPARAELECTRICS WITH DISTRIBUTIONS OF THE LOCAL TRANSITION-TEMPERATURE

A model of relaxors as superparaelectrics with a distribution of the l ocal transition temperature has been investigated. The necessary model parameters are obtained from the analysis of the static polarization response of lead magnesium niobate and then employed in simulations of the frequency-dependent dielectric properties. The present model is c ompared with a previously published model of relaxors, based on a sing le transition temperature but with a distribution of the size of the p olar regions. Both of them describe some characteristic features of re laxors, i.e. the shift of the peaks in temperature dependence of the r eal and imaginary parts of the dielectric permittivity with frequency and the broadening of the relaxation time spectrum on cooling. However , a model which takes into account the distribution of the size of the polar regions describes qualitatively correctly the shape of the rela xation time spectrum.