Sol-gel synthesis and characterization of nanocrystalline (Bi0.5Na0.5)TiO3 powders from the poly vinyl alcohol evaporation route

Nanocrystalline pure perovskite phase bismuth sodium titanate (Bi0.5Na0.5)TiO3(BNT) powders have been prepared by a sol-gel method from the poly vinyl alcohol evaporation route, bismuth nitrate [Bi(NO3)3], tetra-butyl titanate [Ti(OC4H9)4] and sodium acetate(CH3COONa) were used as raw materials and poly vinyl alcohol(PVA) as the sol-gel forming solvent. Stoichiometric amounts of the individual raw materials were thoroughly mixed in accordance with the BNT composition to form the stock solution. The pH of the stock was adjusted to 1-3 by adding acetate. Aqueous solution of PVA[10%(w/v)] was then added to the cationic mixture with thorough stirring. The weight ratio of the cationic mixture to the PVA aqueous solution was maintained at 2:1. The resulting viscous liquid was then heated over a hot crucible up to form a fluffy dry gel. The fluffy dry gels were calcined at different temperatures and times and then cooled to room temperature naturally. The X-ray powder diffraction(XRD) patterns of the heat-treated powders were obtained using a Bruker D8 Advance X-ray diffractometer with Cu Kα radiation and nickel filter. Scanning electron microscope (SEM) studies of the NBT powders were performed using a JSM-6700F electron microscope. Phase-pure BNT powders were obtained at 550 deg. C for 2-2.5h which is relatively lower calcination temperature than other reports. The BNT powders consists of phase-pure perovskite nanocrystals with an average size of 100-200nm.