Large strain under low driving field in lead‐free relaxor/ferroelectric composite ceramics

Abstract 0.75(Na 0.5 Bi 0.5 )TiO 3 –0.25SrTiO 3 lead‐free incipient piezoceramic is a promising candidate for actuator applications due to their large reversible electromechanical strains at the relatively low driving field of 40 kV/cm. In order to further reduce the driving field of 0.75(Na 0.5 Bi 0.5 )TiO–0.25SrTiO 3 relaxor ceramic to meet the requirements for real actuators application, the relaxor/ferroelectric ( RE / FE ) 0‐3 composite ceramics method was employed. The polarization and strain behaviors were examined as a function of the weight ratio of the relaxor/ferroelectric phases. It was found that 90 wt% 0.75(Na 0.5 Bi 0.5 )TiO 3 –0.25SrTiO 3 /10 wt% 0.96(Na 0.84 K 0.16 ) 1/2 Bi 1/2 TiO 3 –0.04SrTiO 3 RE / FE 0‐3 type composite samples provided a high unipolar strain of 0.25% and the corresponding large‐signal piezoelectric coefficient, d * 33 of 833 pm/V at 30 kV/cm, which are 32% higher than the values of the pure 0.75(Na 0.5 Bi 0.5 )TiO 3 –0.25SrTiO 3 . The enhanced electric‐field‐induced strain at relatively lower field was attributed primarily to the reduction in the RE ‐ FE phase transition electric field. It was also found that the RE / FE composite ceramics exhibited significantly reduced frequency dependence in the unipolar strain behavior at room temperature.