Effect of Crystallization Temperature on Energy-Storage Density and Efficiency of Lead-Free Bi0.5(Na0.8K0.2)0.5TiO3 Thin Films Prepared by Sol-Gel Method

Lead-free Bi0.5(Na0.80K0.20)0.5TiO3 (BNKT) ferroelectric films were synthesized on Pt/Ti/SiO2/Si substrates via the chemical solution deposition. The influence of the crystallization temperature on the microstructures, the ferroelectric and energy-storage properties of the films was investigated in detail. The results showed that the BNKT films have reached the well crystallized state in the single-phase perovskite structure at 700 °C. Ferroelectric and energy-storage properties of the films were significantly enhanced by increasing the crystallization temperature. The remnant polarization (2Pr) and maximum polarization (2Pm) reached the highest values of 18.4 μC/cm2 and 61.2 μC/cm2, respectively, under an applied electric field of 300 kV/cm. Thanks to the strong enhancement in 2Pm and the large Pmax - Pr value, the highest energy-storage density (Jreco) and efficiency of 2.3 J/cm3 and 58.2%, respectively, were obtained. These results indicate that the BNKT films have application potentials in advanced capacitors.