Lead-free electrostrictive bismuth perovskite ceramics with thermally stable field-induced strains

Abstract

Electric field-induced strain (EFIS) properties of Bi-1/2(Na0.82K0.18)(1/2)TiO3 (BNKT) ceramics modified with Sr (K1/4Nb3/4)O-3 (SKN) have been investigated as functions of composition and temperature. BNKT ceramics near a phase boundary revealed the coexistence of ferroelectric rhombohedral and tetragonal phases, resulting in a typical ferroclectric butterfly-shaped bipolar S-E loop at room temperature, whose normalized strain (S-max/E-max.) showed a significant temperature coefficient of 0.38 pm/V/K. However, 5 mol% SKN-modified BNKT ceramics revealed a typical electrostrictive behaviour with a thermally stable electrostrictive coefficient, Q(33) = 0.021 m(4)/C-2, which is almost comparable to that of Pb(Mg1/3Nb2/3)O-3 (PMN) ceramics that have been dominantly used as Pb-based electrostrictive materials over the last decades.