Electrical Properties of Lead-Free Ferroelectric Mn-Doped K_0.5Na_0.5NbO₃–CaZrO₃Thin Films Prepared by Chemical Solution Deposition

Abstract

Lead-free ferroelectric K0.5Na0.5NbO3–CaZrO3 thin films were prepared by chemical solution deposition. Chemically optimized K0.5Na0.5NbO3–CaZrO3 precursor thin films crystallized in the perovskite single phase on Pt/TiOx/SiO2/Si substrates at 650 °C. The K0.5Na0.5NbO3–CaZrO3 thin films showed poor ferroelectric polarizations due to the insufficient insulating resistance. The leakage current of the K0.5Na0.5NbO3–CaZrO3 films, especially in the high-applied-field region, was markedly reduced by 1 mol % Mn doping for the Nb site. Also, the ferroelectric properties of the K0.5Na0.5NbO3–CaZrO3 thin films depended on CaZrO3 concentration. 1 mol % Mn-doped K0.5Na0.5NbO3–CaZrO3 thin films exhibited slim and small ferroelectric polarization–electric field (P–E) hysteresis loops at room temperature with an increase in CaZrO3 amount. Furthermore, these films showed a typical field-induced displacement curve with a small hysteresis, and the estimated effective d33 values were 32 pm/V for the 1 mol % Mn-doped 0.95K0.5Na0.5NbO3–0.05CaZrO3 thin films and 21 pm/V for the 1 mol % Mn-doped 0.9K0.5Na0.5NbO3–0.1CaZrO3 thin films.