Study of Structural Phase Transition and Dielectric Behavior Of BiNaTiO 3 -SrTiO3 (BNT-ST) Solid Solution

Abstract

Bismuth sodium titanate (BNT) has been widely recognized as a lead free piezoelectric materials to replace PZT. Doping or substitution with other ferroelectric perovskite has been employed to improve the properties of BNT. In the present attempt, we have developed SrTiO 3 as a dopant to enhance dielectric behavior of BNT. (1-x)BiNaTiO3-x SrTiO3 (BNT-ST) solid solution x=0.24, 0.25, 0.26, 0.27, and 0.28 are synthesized by hydrothermal combustion method using metal nitrates, nitric acid and citric acid as a fuel. The structures of as-synthesized compositions of BNT-ST were confirmed by X-ray diffraction (XRD). XRD patterns for the composition (1-x) BiNaTiO 3-x SrTiO3 [for x= 0.24] are matched with rhombohedral phase of BNT; however with the increasing ST concentration (x > 0.24) phase transition from rhombohedral-to-cubic are induced. For composition x = 0.25-0.26, both the phases are coexisted i.e rhombohedral and cubic phase. It clearly indicates that morphotropic phase boundary is developed in BNT-ST for ST composition between 0.25-0.26. These are also confirmed by RAMAN spectroscopy. The morphotropic phase boundary is the desired conditions for enhancement of dielectric and piezoelectric behavior. Enhancement of dielectric constant for these compositions is also observed.