Influence of Crystallization Time on Energy-Storage Density and Efficiency of Lead-Free Bi0.5(Na0.8K0.2)0.5TiO3 Thin Films

Abstract

Lead-free Bi0.5(Na0.80K0.20)0.5TiO3 (BNKT) ferroelectric films were synthesized on Pt/Ti/SiO2/Si substrates via chemical solution deposition. The influence of crystallization time on the microstructures and ferroelectric and energy-storage properties of the films was investigated in detail. The XRD analysis showed that the BNKT films have well crystallized corresponding to the single-phase perovskite structure at 700°C. Ferroelectric and energy-storage properties of the films were significantly enhanced by increasing crystallization time. With crystallization time of 60 min, the remnant polarization (Pr), maximum polarization (Pm), and Pm-Pr values reached the highest values of 7.9 µC/cm2, 28.9 µC/cm2, and 21.0 µC/cm2, respectively, under the electric field of 400 kV/cm. Thanks to the strong enhancement in Pm and the large Pma-Pr value, the highest recoverable energy-storage density (Jreco) gets the value of 2.9 J/cm3. The obtained results indicate that the BNKT films have application potentials in advanced capacitors.