Electrical Properties of Lead-Free Ferroelectric Mn-Doped K0.5Na0.5NbO3--CaZrO3 Thin Films Prepared by Chemical Solution Deposition

Lead-free ferroelectric K 0.5 Na 0.5 NbO 3 --CaZrO 3 thin films were prepared by chemical solution deposition. Chemically optimized K 0.5 Na 0.5 NbO 3 --CaZrO 3 precursor thin films crystallized in the perovskite single phase on Pt/TiO x /SiO 2 /Si substrates at 650 °C. The K 0.5 Na 0.5 NbO 3 --CaZrO 3 thin films showed poor ferroelectric polarizations due to the insufficient insulating resistance. The leakage current of the K 0.5 Na 0.5 NbO 3 --CaZrO 3 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 K 0.5 Na 0.5 NbO 3 --CaZrO 3 thin films depended on CaZrO 3 concentration. 1 mol % Mn-doped K 0.5 Na 0.5 NbO 3 --CaZrO 3 thin films exhibited slim and small ferroelectric polarization--electric field ($P$--$E$) hysteresis loops at room temperature with an increase in CaZrO 3 amount. Furthermore, these films showed a typical field-induced displacement curve with a small hysteresis, and the estimated effective $d_{33}$ values were 32 pm/V for the 1 mol % Mn-doped 0.95K 0.5 Na 0.5 NbO 3 --0.05CaZrO 3 thin films and 21 pm/V for the 1 mol % Mn-doped 0.9K 0.5 Na 0.5 NbO 3 --0.1CaZrO 3 thin films.