Preparation and properties of sol–gel-derived Bi0.5Na0.5TiO3 lead-free ferroelectric thin film

Polycrystalline ferroelectric lead-free Bi0.5Na0.5TiO3 (BNT) thin films have been successfully deposited on Pt/Ti/SiO2/Si substrates by an improved sol–gel process using rapid thermal annealing. Our results indicate that thermal annealing in an oxygen atmosphere after each layer of coating is effective in promoting crystallization of the film at a relatively low temperature of 650 °C. The resulting film is dense and well crystallized in the rhombohedral perovskite phase, and has good electrical and ferroelectric properties. The observed dielectric constant and loss at 100 kHz are 277 and 0.02, respectively, while the observed remanent polarization and coercive field under an alternating current electric field of 1100 kV/cm are 8.3 μC/cm2 and 200 kV/cm, respectively. The BNT based film is expected to be a promising candidate for lead-free piezoelectric applications.