Influence of Crystallization Temperature on Structural, Ferroelectric, and Ferromagnetic Properties of Lead-Free Bi0.5(Na0.8K0.2)0.5TiO3 Multiferroic Films

Lead-free Bi-0.5(Na0.8K0.2)(0.5)TiO3 (abbreviated as BNKT) films have been synthesized via a sol-gel technique on Pt/Ti/SiO2/Si substrates, and the dependence of the physical properties in BNKT films were investigated as a function of the crystallization temperature. The BNKT films were annealed at different temperatures (600, 650, 700, and 750 degrees C) for 60min in the air. The results of this study showed that the optimal crystallization temperature is 700 degrees C. At this, the BNKT films exhibited a single perovskite phase structure and high-dense surface. Besides, the remanent (P-r) and maximum (P-m) polarization reached their highest values of 9.2 mu C/cm(2) and 30.6 mu C/cm(2), respectively. All the films showed a weak ferromagnetic behavior with the maximum saturated magnetization (M-s) of 2.1emu/cm(3). These values are equivalent to the highest P-r and P-m values in previous reports on lead-free films.