Dielectric, ferroelectric and field induced strain properties of Nb-modified Pb-free 0.99Bi0.5(Na0.82K0.18)0.5TiO3-0.01LiSbO3 ceramics

The effect of Nb-substitution on the dielectric, electromechanical and piezoelectric properties of Pb-free 0.99[Bi-1/2(Na0.82K0.18)1/2Ti(1-x)Nb(x)O(3)]-0.01LiSbO(3) (x = 0-0.05) piezoelectric ceramics has been investigated. X-ray diffraction analysis reveals the formation of single-phase perovskite structure with tetragonal symmetry for the compositions with x <= 0.025. Both the dielectric constant and depolarization temperature decreased with an increase in Nb-content. Analysis of the electric-field-induced polarization and strain hysteresis loops indicated that Nb substitution disrupted the long range ferroelectric order of BNKT-LS ceramics. This degraded the remnant polarization, coercive field and piezoelectric coefficient d(33) while the electric-field-induced strain increased (peaked at x = 0.015) to 0.43% corresponding to a normalized strain (d(33)*) of 614 pm/V at a deriving field of 7 kV/mm. This abnormal strain enhancement may be attributed to the coexistence of ferroelectric (FE) and relaxor ferroelectric (RFE) phases. (c) 2013 Elsevier B.V. All rights reserved.