A monoclinic to tetragonal crossover in (Na0.5Bi0.5TiO3)(1−x)(BaZrO3)xceramic: a lead-free ferroelectric material

Abstract

A single-phase solid solution of Na0.5Bi0.5TiO3(NBT) and BaZrO3(BZ),i.e.(NBT)(1−x)(BaZrO3)x(x= 0.00, 0.01, 0.03, 0.05 and 0.07), was synthesized using the solid-state reaction method. It is found that the temperature for single-phase formation increases with increasing BZ content. A detailed structural investigation was carried out as a function of composition using Rietveld analysis of powder X-ray diffraction data. The structural refinement reveals a crossover from monoclinic (Cc) to tetragonal (P4mm) symmetry in the composition range 0.03 <x< 0.05. The intensity of superlattice reflection due toa−a−c−tilting of oxygen octahedra in theCcphase was found to decrease with increasing BZ content. The unit-cell volume was also found to increase with BZ content, which was attributed to the higher ionic radii of Ba2+and Zr4+in comparison to Bi3+(Na+) and Ti4+. The structural phase boundary observed in (NBT)(1−x)(BaZrO3)xis concurrent with the observation of morphotropic phase boundary like behaviour.