Effect of direct-current biasing on the dielectric properties of barium strontium titanate

Abstract

Ba1-xSrxTiO3 (BST, x = 0 to x = 1) ferroelectric ceramics doped with 1.0 mol% MgO and 0.05 mol% MnO2 were prepared with a rate-controlled sintering profile, As the strontium molar fraction x increased, the average grain size decreased from 14 mu m for x = 0 to 2 mu m for x = 1, Temperature dependence of the dielectric properties was measured as a function of de biasing, At 10 degrees C above the Curie temperature, the changes of dielectric constant at 5000 V/cm were 28%, 17%, 26%, and 36% for x = 0, 0.25, 0.5, and 0.75, respectively, The reduction of dielectric constant by the applied de biasing was fitted by a phenomenological equation that was based on Devonshire's theory, From this phenomenological equation, an anharmonic coefficient, which was an order parameter of the anharmonic interactions, was calculated for each composition, As the strontium molar fraction increased, these coefficients increased from 2.45 x 10(-19) cm(2).V-2 for x = 0 to 5.90 x 10(-19) cm(2).V-2 for x = 0.75, A similar trend was observed on the de field dependence of the dielectric loss, except at high field for x = 0, of which a high loss was obtained, A two-element circuit model was proposed to explain the effect of high de biasing on the dielectric loss.