Strain enhancement in Bi1/2(Na0.82K0.18)1/2TiO3 lead-free electromechanical ceramics by co-doping with Li and Ta

The effects of co-doping with Ta- and Li-ions on the microstructure, crystal structure, ferroelectric, and electric field-induced strain properties of Bi-1/2(Na0.82K0.18)(1/2)TiO3 (BNKT) ceramics were investigated. Li substitution into Na-sites led to a ferroelectric-nonpolar phase transition and a large accompanying normalized strain (S-max/E-max) of 727 pm/V near the phase boundary, when 2.5 mol% Li and 2.5 mol% Ta were co-doped on A- and B-sites, respectively. The phase transition-related strain was thought to be induced by a decrease in the tolerance factor of the perovskite structure. (C) 2011 Elsevier B.V. All rights reserved.