Lead-free Bi1/2(Na0.82K0.18)1/2TiO3 relaxor ferroelectrics with temperature insensitive electrostrictive coefficient

The electric field-induced strain of Bi1/2(Na0.82K0.18)1/2TiO3 (BNKT) ceramics modified with BaZrO3 (BZ) was investigated as a function of composition and temperature. Unmodified BNKT ceramics revealed a typical ferroelectric butterfly-shaped bipolar S–E loop at room temperature, whose normalized strain (Smax/Emax) showed a significant temperature coefficient of 0.38 pm/V/K. As the BZ content increased in the solid solution up to 5 mol%, the ferroelectric BNKT gradually transformed to a relaxor. Finally, 5 mol% BZ-modified BNKT ceramics showed a typical electrostrictive behavior with a thermally stable electrostrictive coefficient (Q33) of 0.025 m4/C2, which is comparable to that of Pb(Mg1/3Nb2/3)O3 (PMN) ceramics that have been primarily used as Pb-based electrostrictive materials.