Effect of titanium substitution on film structure and ferroelectric properties of Sr-deficient Sr_0.75Bi_2.35Ta₂O₉ thin films

Ferroelectric films of bismuth-containing layered perovskite Sr_0.75Bi_2.35(Ta_2-xTi_x)O₉ (x = 0-0.8) have been prepared using a metal-organic decomposition method. The effects of Ti substitution on the microstructure evolution and ferroelectric properties of Sr_0.75Bi_2.35Ta₂O₉ films were investigated. A maximum remanent polarization of 2P_r = 30.7 μC/cm² was obtained for the Sr_0.75Bi_2.35Ta_1.8Ti_0.2O₉ film as compared to Sr_0.75Bi_2.35Ta₂O₉ films (19.6 μC/cm²) annealed at 800 °C in air. The Ti substitution for Ta leads to charge compensation for the self-produced positive Bi_Sr^. due to the occupation of Bi on Sr vacancies and is responsible for the increase in leakage resistance. The leakage current density as low as 2 × 10^-8 A/cm² can be obtained at an applied electric field of 100 kV/cm. Substitution of Ti for Ta shows a positive effect on the fatigue endurance of Sr-deficient Sr_0.75Bi_2.35Ta₂O₉ film.