Ferroelectric and piezoelectric properties of La-modified lead-free (Bi0.5Na0.5)TiO3-(Bi0.5K0.5)TiO3-SrTiO3 thin films

Lead-free piezoelectric 0.9(0.8Bi(0.5)Na(0.5)TiO(3)-0.2Bi(0.5)K(0.5)TiO(3))-0.1SrTiO(3) thin films doped with x mol% La (abbreviated as BNT-BKT-ST-xLa) (x=0, 0.5, 1.0, 1.5) were prepared by a sol-gel method on Pt(1 1 1)/Ti/SiO2/Si substrates. The effects of La content on the microstructure, ferroelectric and piezoelectric properties were investigated systematically. The X-ray diffraction patterns indicated that all films had a single-phase perovskite structure. Meanwhile, we found that lanthanum content had great influence on the grain size and electrical properties. The thin film with a composition of BNT-BKT-ST-0.5La showed the optimal electrical properties with a remnant polarization, dielectric constant and effective piezoelectric constant of 10 mu C/cm(2), 560, and 83 pm/V, respectively. The results indicated that 0.5 mol% La-doped BNT-BKT-ST thin films would be of great interest for lead-free piezoelectric devices. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.