Phase structure, microstructure and piezoelectric properties of perovskite (K0.5Na0.5)0.95Li0.05NbO3-Bi0.5(K0.15Na0.85)0.5TiO3 lead-free ceramics

Lead-free ceramics (1-x)(K0.5Na0.5)(0.95)Li0.05NbO3-xBi(0.5)(K0.15Na0.85)(0.5)TiO3 [(1-x)KNLN-xBKNT] with x=0-0.04 were successfully synthesized by conventional solid-state sintering. Effects of Bi-0.5(K0.15Na0.85)(0.5)TiO3 (BKNT) on the phase structure, microstructure and electrical properties of the (1-x)KNLN-xBKNT ceramics were investigated. BKNT strongly affected the sintering behavior, densification and microstructure of the ceramics. X-ray diffraction analysis revealed that all the (1-x)KNLN-xBKNT ceramics possessed pure perovskite structure, showing symmetries of orthorhombic at x < 0.005, and tetragonal at x >= 0.015 at room temperature. Coexistence of orthorhombic and tetragonal phases was identified in the range of 0.005 <= x < 0.015. The 0.99KNLN-0.01BKNT ceramics showed the optimum piezoelectric, ferroelectric properties and high Curie temperature, which were as follows: d(33) = 240 pC/N, k(p) = 0.455, p(r) = 20 mu C/cm(2), E-c = 20.8 kV/cm and T-c = 469 degrees C. The mechanism of the enhanced piezoelectric properties was also discussed. These results indicate that this system looks a promising candidate for lead-free piezoelectric materials. (C) 2010 Elsevier B.V. All rights reserved.