Growth and Ferroelectric Behaviors of (Na_0.5Bi_0.5)TiO₃ Thin Films

抄録

Lead-free piezoelectric/ferroelectric sodium bismuth titanate (Na_0.5Bi_0.5)TiO₃ in thin film form has never been studied properly, although (Na_0.5Bi_0.5)TiO₃ ceramic has been widely investigated. In this paper, a systematic study is presented of the successful growth and ferroelectric behaviors of polycrystalline (Na_0.5Bi_0.5)TiO₃ thin films by RF magnetron sputtering, whereby a number of synthesis parameters were examined for their effects on the phase and structural developments of thin films. The ferroelectric thin films exhibit well-defined hysteresis loop, with a remanent polarization (P_r) of 11.9 μC/cm² and coercive field (E_c) of 37.9 kV/cm. They show ~4% and 20% of decrease in polarization after 10⁸ and 10¹⁰ cycles of switching cycles, respectively. There occurs a steady decrease in dielectric constant in the range of 400 to 250 over the frequency range of 10²-10⁵ Hz. The effects of mobile and highly electropositive alkali Na⁺ on the ferroelectric properties of (Na_0.5Bi_0.5)TiO₃ thin films are discussed.