Synthesis of BiFeO3-Bi0.5Na0.5TiO3 Thin Films by Chemical Solution Deposition and Their Properties

Multiferroic BiFeO3-Bi0.5Na0.5TiO3 thin films were synthesized on Pt/TiOx/SiO2/Si substrates by chemical solution deposition. When the amount of Bi0.5Na0.5TiO3 exceeded 30 mol %, perovskite BiFeO3-Bi0.5Na0.5TiO3 single phase thin films were successfully fabricated in the temperature range of 550-700 degrees C. Also, the surface morphology of the 0.7BiFeO(3)-0.3Bi(0.5)Na(0.5)TiO(3) thin films was improved by optimizing the amounts of excess Bi and Na in 0.7BiFeO(3)-0.3Bi(0.5)Na(0.5)TiO(3) precursor solutions. However, measurements of ferroelectric polarization-electric field hysteresis loops were difficult for 0.7BiFeO(3)-0.3Bi(0.5)Na(0.5)TiO(3) thin films due to the large leakage current densities at room temperature. At low temperatures, the 0.7BiFeO(3)-0.3Bi(0.5)Na(0.5)TiO(3) thin films demonstrated improved insulating resistance and exhibited potential ferroelectric properties. Furthermore, by Mn doping of the 0.7BiFeO(3)-0.3Bi(0.5)Na(0.5)TiO(3) films, improved ferroelectric properties with weak ferromagnetism were achieved at room temperature. In 0.7Bi(Fe-0.Mn-95(0).(05))O-3-0.3Bi(0.5)Na(0.5)TiO(3) thin films, ohmic conduction was dominant in an electric field range of 0-200 kV/cm and the abrupt increase in leakage current was suppressed even at high electric fields, whereas nondoped 0.7BiFeO(3)-0.3Bi(0.5)Na(0.5)TiO(3) films exhibited nonohmic conduction with a larger leakage current. The remanent polarization and coercive field of the 0.7Bi(Fe0.95Mn0.05)O-3-0.3Bi(0.5)Na(0.5)TiO(3) films at room temperature were approximately 26 mu C/cm(2) and 250 kV/cm, respectively. (C) 2011 The Japan Society of Applied Physics