Enhanced piezoelectric properties near the morphotropic phase boundary in lead-free (1-x)(Bi0.5K0.5)TiO3-xBi(Ni0.5Ti0.5)O3 ceramics

Lead-free piezoelectric ceramics of the composition (1-x)(Bi0.5K0.50)TiO3-xBi(Ni0.50Ti0.50)O-3 or (1-x) BKT-xBNiT (when x = 0-0.20 mol fraction) were prepared by a conventional mixed-oxide method and sintered at 1050 degrees C for 4 h. The effects of BNiT content on the phase equilibria, and the dielectric, ferroelectric and piezoelectric properties were systematically investigated. High density sintered specimens (5.71-6.12 g/cm(3)) were obtained for all compositions. X-ray diffraction patterns showed that all BKT-BNiT samples exhibited a single perovskite phase which confirms that BNiT and BKT formed a solid solution up to x = 0.20. A morphotropic phase boundary (MPB) separating a BKT-rich tetragonal phase and a BNiT pseudo-cubic phase was identified over the compositional range 0.05 < x < 0.10, where enhanced electrical properties were observed. The optimum dielectric properties (er = 1710, tan delta = 0.036), ferroelectric properties (P-r = 16.6 mu C/cm(2), E-c = 22.5 kV/cm and R-sq = 0.86) and piezoelectric properties (d(33) = 288 pC/N, S-max = 0.22% and d*(33) = 313 pm/V) were observed with a relatively high T-m similar to 304 similar to C within this MPB region. Overall, these results indicate that the BKT-BNiT ceramic system is a promising lead-free piezoelectric candidate for further development for actuator applications. (C) 2015 Elsevier B.V. All rights reserved.