Piezoelectric and Dielectric Properties of (Na0.5K0.5)NbO3-(Bi0.5Na0.5)0.94Ba0.06TiO3 Lead-Free Piezoelectric Ceramics

Lead-free piezoelectric ceramics (1 - x)(Na0.5K0.5)NbO3-x(Bi0.5Na0.5)(0.94)Ba0.06TiO3 (abbreviated as NKN-BNBT100x, x = 0-0.10) were fabricated by a conventional mixed oxide route, and the effects of BNBT on electrical properties and crystal structures were investigated. X-ray diffraction analysis results indicate that BNBT diffuses into the NKN lattice to form a solid solution during sintering. All samples show pure perovskite structures and an orthorhombic-tetragonal phase transition with increasing x. The tetragonality, however, declined with further increasing x. The dielectric and piezoelectric properties are enhanced for the composition near the orthorhombic-tetragonal morphotropic phase boundary. The NKN-BNBT4 ceramics show good performance with piezoelectric constant d(33) = 256 pC/N, planar electromechanical coupling factor k(p) = 43%, and dielectric constant epsilon(T)(33)/epsilon(0) = 875. The results reveal that (1 - x)(Na0.5K0.5)NbO3-x(Bi0.5Na0.5)(0.94)Ba0.06TiO3 ceramics are promising candidate materials for lead-free piezoelectric application. (C) 2009 The Japan Society of Applied Physics