STRUCTURAL, FERROELECTRIC AND ENERGY-STORAGE PROPERTIES OF LEAD-FREE Zr-DOPED Bi0.5(Na0.80K0.20)0.5TiO3 FILMS

Perovskite-type lead-free Bi-0(.5)(Na0.80K0.20)(0.)(5)(Ti1-xZrx)O-3 (BNKT-xZr) ferroelectric films (with x from 0.00 to 0.05) were synthesized on Pt/Ti/SiO2/Si substrates via chemical solution deposition. The influence of Zr4+ concentration on the microstructures, ferroelectric and energy-storage properties of the prepared films was investigated in detail. It showed that the BNKT-xZr films possessed rhombohedral and tetragonal symmetries in morphotropic phase boundary when a small amount of Zr4+ was added. Ferroelectric and energy-storage properties of the films investigated at an applied electric field of 600 kV/cm were significantly enhanced with appropriate Zr4+ concentration. The remnant polarization (P-r), maximum polarization (P-max) and P-max-P-r values at x = 0.02 reached the highest values of 18.1 mu C/cm 2 , 42.0 mu C/cm(2) and 24.0 mu C/cm(2), respectively. Thanks to the strong enhancement in P-max and the large P-max-P-r value, the highest recoverable energy-storage density gets the value of 4.6 J/cm(3) for the 2 mol.% Zr4+-doped BNKT film. These obtained results indicate that the appropriate Zr4+-doped BNKT films have many application potentials in the advanced capacitors.