Bipolar Electric Field Induced Strain in Li Substituted Lead-Free Bi0.5(Na0.82K0.18)0.5Ti0.95Sn0.05O3 Piezoelectric Ceramics

We have fabricated environmental friendly lead-free Bi-0.5(Na0.82K0.18)(0.5)TiO3 (BNKT) and Bi-0.5(Na(0.82-x)LixK0.18)(0.5)(Ti0(.95)Sn(0.05))O-3 piezoelectric ceramics (BNKTS-xLi) with x ranging from 0 to 0.05 by the conventional solid state reaction method. The effects of Li substitution were studied through the crystal structures and the piezoelectric properties. The X-ray diffraction data showed that BNKTS-xLi ceramics experienced a phase transition from the pseudocubic phase to the rhombohedral and tetragonal symmetry when the Li doping content increased. The typical butterflyshaped bipolar S-E loops of piezoelectric materials were observed in all compositions. The small amount of Li substitution for BNKTS-xLi ceramics led to a marked enhancement in piezoelectric properties, with the electric field-induced strain (S-max/E-max) reaching the highest value of 590 pm/V at x = 0.04. The BNKTS-xLi ceramics will be excellent candidates for applications in lead-free ferroelectric and piezoelectric devices.