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_0.5Bi_0.5)_1+x TiO₃ (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_0.5Bi_0.5TiO₃ 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_0.51Bi_0.51TiO₃ sample with x = 0.02 exhibits better structural, dielectric and ferroelectric properties in whole range of sintering temperature.

KEYWORDS:

• Lead free NBT ceramic
• Na/Bi non-stoichiometry
• Sintering temperature
• Sol-gel
• Structural
• Dielectric
• Ferroelectric properties

Acknowledgement

One of the authors (K. Parmar) is grateful to UGC, New Delhi for providing financial assistance by UGC (BSR) under grants No: F.11-83/2008 (BSR).