Tailoring structural and electrical properties of A-site non-stoichiometric Na_0.5Bi_0.5TiO₃ ceramic at different sintering temperature

Abstract

Na/Bi stoichiometry plays crucial role in determining various properties of sodium bismuth titanate-based system. In this work, we have synthesised lead free (Na 0.5 Bi 0.5 ) 1+x TiO 3 (x = 0, 0.02 and 0.05) ceramics by sol-gel method and systematically presented structural, dielectric and ferroelectric properties at different sintering temperature. Single phase perovskite structure with rhombohedral symmetry (R3c) is obtained for all compositions from low (850°C) to maximum (1150°C) sintering temperature. The shifting of x-ray diffraction peaks and characteristic perovskite metal-oxide vibrational band (∼627 cm −1 ) in Fourier Transform Infra-red spectra suggests compression or expansion of crystal lattice with Na/Bi non-stoichiometry. Excess of Na/ Bi comprises dense crystal growth as compared to pure Na 0.5 Bi 0.5 TiO 3 composition suggesting compensation of volatile elements loss during heat treatment whose impact has also been observed in dielectric as well as ferroelectric properties. It is observed that Na 0.51 Bi 0.51 TiO 3 sample with x = 0.02 exhibits better structural, dielectric and ferroelectric properties in whole range of sintering temperature.