Electromechanical and ferroelectric properties of (Bi1/2Na1/2)TiO3-(Bi1/2K1/2)TiO3-BaTiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (0.95-x)(Bi1/2Na1/2)TiO3-x(Bi1/2K1/2)TiO3-0.05BaTiO(3) (abbreviated as BNT-BKT-BT100x, with x ranged from 0 to 20 mol %) have been studied. Effects of amount of BKT on the electrical properties and crystal structure were examined. BNT-BKT-BT5 ceramics give good performances with piezoelectric constant d(33)=148 pC/N, electromechanical coupling factor k(p)=34 %, k(t)=49.2 %, free permittivity epsilon(33)(T)/epsilon(0)=700, and dissipation factor tandelta=2 % at 1 kHz. Accordingly, the sample shows larger remanent polarization and lower coercive field than 0.95BNT-0.05BT ceramics. X-ray diffraction analysis shows that incorporated BKT diffuses into the BNT-BT lattice to form a solid solution during sintering, but changes the crystal structure from rhombohedral to tetragonal symmetry at higher BKT amounts. (C) 2004 American Institute Of Physics.