The effect of Ba/Sr ratio on the Curie temperature for ferroelectric barium strontium titanate ceramics

Abstract

The powders of lead-free material namely (nonhazardous) barium strontium titanate (BST) with different stoichiometric compositions have been synthesized by the sol–gel method. Ba[Formula: see text]Sr[Formula: see text]TiO3 (BST) materials possess the properties of both ferroelectric and dielectric materials. These materials have spontaneous polarization that can be reversed by an applied electric field and they remain polarized even when the applied external electric field is removed. Synthesized samples have been subjected to structural, morphological, and dielectric characterizations. In this study, BST nanopowders with different substitutions of [Formula: see text] (where [Formula: see text]= 0.2, 0.3, 0.4, 0.5, and 0.6) were prepared by the sol–gel method, which is an easy method with low power consumption and low temperature requirement and produces higher yield. Nanopowders had average particle sizes of 12–24 nm and particles sizes after sintering at 1000[Formula: see text]C for 3 h were 197, 267, 79.80, 63.09, and 63 nm. All resulting pellets had a polycrystalline structure. Crystal structure, space group, morphological characterization, and particle size were determined from the structural analysis using X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The dielectric measurements were made for BST pellets under different frequencies (1–200 kHz) from room temperature to 250[Formula: see text]C. The dielectric constants for the bulk were 743, 1566, 1091, 766, and 626 for [Formula: see text]= 0.2, 0.3, 0.4, 0.5, and 0.6, respectively. From dielectric measurements, samples with [Formula: see text]= 0.2 and 0.3 had the Curie temperatures of 70[Formula: see text]C and 28.5[Formula: see text]C, respectively, and remained intact below 0[Formula: see text]C. The sample with [Formula: see text]= 0.3 had a good dielectric measurement and moderate dissipation factor; it may be used in capacitance application as energy stores.