Reduced leakage current, enhanced ferroelectric and dielectric properties of (La, Fe)-codoped Bi0.5Na0.5TiO3-based thin films

The lead-free Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3–SrTiO3 (BNT–BKT–ST) and (La, Fe)-codoped Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3–SrTiO3 (BNT–BKT–ST–LaFe) thin films were deposited on Pt/Ti/SiO2/Si substrates by the sol–gel method. Both the BNT–BKT–ST and BNT–BKT–ST–LaFe thin films exhibit pseudo-cubic perovskite structure and uniform grain size. The leakage current density of BNT–BKT–ST–LaFe thin film at 400 kV/cm is reduced by approximately two orders of magnitude compared with BNT–BKT–ST thin film. Enhanced ferroelectric property is achieved in BNT–BKT–ST–LaFe film with a large remanent polarization of 13 μC/cm2. At the same time, the BNT–BKT–ST–LaFe film also exhibits a large dielectric constant of 420 and small dielectric loss of 0.055 at 100 kHz. These results indicate that the (La, Fe)-codoped BNT–BKT–ST thin film is a promising candidate in lead-free ferroelectric materials.