The synthesis of lead-free ferroelectric Bi1/2Na1/2TiO3 thin film by solution-sol-gel method

Bi1/2Na1/2TiO3 (described as BNT) is considered as a promising lead-free ferroelectric material. In this study, BNT sol was synthesized by mixing bismuth oxide and sodium carbonate dissolved in nitric acid and titanium tetraisopropoxide in ethylene glycol, which was called a solution-sol-gel method and very cost-effective synthesis method, while very high-cost metal alkoxides are used as precursors in conventional sol-gel method. FT-IR and Raman analyses indicated that the chemical modification of titanium tetraisopropoxide by glycolic acid or oxalic acid occurred and the synthesis of stable BNT sol was possible. In the results of high temperature X-ray analysis and DTA/TG analyses, the crystallization of BNT was thought to occur at between 500 and 700 degrees C following the evaporation of solvent and organics and poly-condensation processes. The main crystal phase of the film was identified as rhombohedral crystal phase of Bi1/2Na1/2TiO3 by XRD and Raman spectroscopy analyses, although a small amount of Bi4Ti3O12 existed as a second phase.