The synthesis of lead-free ferroelectric Bi_1/2Na _1/2TiO₃ thin film by solution-sol-gel method

Bi_1/2Na_1/2TiO₃ (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°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 Bi_1/2Na_1/2TiO₃ by XRD and Raman spectroscopy analyses although a small amount of Bi ₄Ti₃O₁₂ existed as a second phase.