Analysis of the dielectric characteristics for polycrystalline Ba0.65Sr0.35TiO3 (I)-frequency dependence in the paraelectric state

The frequency and d.c. field dependences of dielectric properties of Ba0.65Sr0.35TiO3 (BST) with various grain sizes (0.87 mum to 5.43 mum) have been studied in the paraelectric state. The frequency response is analyzed by two approximated power laws obtained on the basis of the Cole-Cole expression. The distribution of relaxation times in BST is broader for specimens with finer grains. The d.c. field is found to affect the static permittivity epsilon (0) rather than the distribution of relaxation times. The effect of the d.c. field on the dielectric permittivity is suppressed for samples with smaller grains and transition broadening is presumed to cause this suppression. It is concluded that both the temperature dependence and the frequency response of the dielectric characteristics of Ba0.65Sr0.35TiO3 are suppressed by the transition broadening. (C) 2000 Kluwer Academic Publishers.