Effect of sintering optimization on the electrical properties of bulk Ba xSr 1−xTiO 3 ceramics

Abstract

Ba x Sr 1− x TiO 3 ( x=0.6, 0.75, 0.80, 0.85 and 0.9) compositions are prepared by solid-state reaction route using controlled heating and cooling. Density optimization by varying sintering temperature was achieved. X-ray diffraction (XRD) analysis shows the phase pure materials. The lattice constant decreases from 3.9868 Å ( x=0.90) to 3.9449 Å ( x=0.60) with increasing Sr 2+; the tetragonal distortion also decreases. Dielectric constant show sharp peaks for samples having low strontium content (0.10, 0.15) and gets smeared out as the strontium content is increased (0.20, 0.25). For further higher Sr 2+ composition (0.40), the dielectric peak could not be observed in the measured temperature range. The peak broadening in Sr 2+ rich compositions indicates that diffused transitions and is attributed to the disorder in the arrangement of cations at A-site. A modified Curie–Weiss law using exponent γ and diffuseness parameter δ fits temperature dependence of dielectric constant in paraelectric phase. Both the parameters increase with increasing Sr 2+ content showing that with strontium substitution, the material becomes disordered and may be correlated with the compositional fluctuation in solid solution. Frequency dependence of dielectric behavior is analyzed in terms of Debye formalism and nature of dielectric relaxation processes is explored using Cole–Cole formalism. Ferroelectric hysterisis loops reveal spontaneous polarization and coercive field increases with deceasing Sr content.