Large electric field-induced strain and piezoelectric responses of lead-free Bi0.5(Na0.80K0.20)0.5TiO3-Ba(Ti0.90Sn0.10)O3 ceramics near morphotropic phase boundary

Abstract

Lead-free piezoelectric ceramics with compositions belonging to family of compositions (1−x)Bi0.5(Na0.80K0.20)0.5TiO3-xBa(Ti0.90Sn0.10)O3 or (1−x) BNKT-xBTS (when x = 0.05 − 0.15 mol fraction) near the morphotropic phase boundary (MPB) were fabricated by a conventional mixed oxide method. Sintered samples had relative densities greater than 98% of their theoretical values. X-ray diffraction data revealed that the MPB region consisted of coexisting rhombohedral and tetragonal phases in the BNKT-BTS system was identified over the entire compositional range. A large electric field-induced strain (Smax) of 0.36% and a normalized strain coefficient (d*33) of 649 pm/V were observed in the BNKT-0.05BTS sample. The sample close to the MPB composition (BNKT-0.11BTS) exhibited the maximum dielectric constant (er = 1770), temperature of maximum permittivity (Tm = 333C°) and low-field piezoelectric coefficient (d33 = 227 pC/N), along with reasonable ferroelectric properties (Pr = 20.6 mC/cm2, Rsq = 0.88) and strain properties (d*33 = 445 pm/V and Smax = 0.24%).