Structural Optimization of Bismuth Sodium Titanate Thin Films

Abstract

Lead-free ferroelectric oxide materials have attracted considerable attention from the environmental viewpoint. Among lead-free piezoelectric materials, bismuth sodium titanate (Bi_0:5Na_0:5TiO₃) is considered to be one of the excellent candidates. The crystal structures, phase transitions and physical properties of BNT in bulk have been widely investigated. However, BNT in thin film form has been rarely reported. In the present work, bismuth sodium titanate (Bi_0.5Na_0.5TiO₃) thin films, synthesized by spin coating technique on alumina substrates, are annealed at different temperature from 100°C to 500°C to optimize the crystal structure. The structurally optimized BNT thin film is observed at 400°C which is confirmed by X-ray diffraction patterns and FWHM calculation of (012) peak. The crystallinity of BNT thin films increases with the increase of annealing temperature and exhibits a single phase of perovskite structure at annealing temperature of 400°C which is also confirmed by scanning electron micrographs. The dielelectric constant also increases with increase of annealing temperature and becomes maximum at 400°C while dielectric loss decreases with increase of annealing temperature and becomes minimum at annealing temperature 400°C which also confirms that the film deposited at 400°C is optimized.

Keywords:

• RXD
• dielectric constant
• SEM
• lead-free oxides