Effects of BaTiO3 Content and Mn Doping on Ferroelectric Properties of NaNbO3-BaTiO3 Thin Films Prepared by Chemical Solution Deposition

Lead-free ferroelectric NaNbO3-BaTiO3 thin films were prepared by chemical solution deposition. Perovskite single-phase NaNbO3-BaTiO3 thin films were successfully fabricated at 550 degrees C on Pt/TiOx/SiO2/Si substrates. The ferroelectric properties of the NaNbO3-BaTiO3 thin films depended on the BaTiO3 content of NaNbO3-BaTiO3. Among NaNbO3-BaTiO3 films with various BaTiO3 concentrations, the 0.95NaNbO(3)-0.05BaTiO(3) thin films showed relatively large polarization at -190 degrees C, although the insulating resistance of the films was not sufficiently high at room temperature. To improve the electrical resistivity at ambient temperatures, Mn doping of 0.95NaNbO(3)-0.05BaTiO(3) was examined. The leakage current density of the films was found to be greatly reduced by a small amount of Mn doping. 1.0 mol % Mn-doped 0.95NaNbO(3)-0.05BaTiO(3) thin films showed well-shaped slim ferroelectric polarization-electric field (P-E) hysteresis loops at room temperature. The remanent polarization (P-r) and coercive field (E-c) values of the 1.0 mol% Mn-doped 0.95NaNbO(3)-0.05BaTiO(3) thin films at 1 kHz were approximately 5 mu C/cm(2) and 50 kV/cm, respectively. Furthermore, the ferroelectric P-E loops of the 1.0 mol% Mn-doped 0.95NaNbO(3)-0.05BaTiO(3) thin films showed good frequency dependence and could be characterized at a frequency as low as 1 Hz. (C) 2009 The Japan Society of Applied Physics