Large electric-field-induced strain in Zr-modified lead-free Bi 0.5(Na 0.78K 0.22) 0.5TiO 3 piezoelectric ceramics

Abstract

Lead-free Zr-modified Bi 0.5(Na 0.78K 0.22) 0.5TiO 3 ceramics (BNKTZ-100 x, with x = 0–0.05) were synthesized by a conventional ceramic fabrication process and its influence on crystal structure and electromechanical properties was investigated. The temperature-dependent dielectric peaks of the BNKTZ-100 x ceramics broadened and ferroelectric polarizations decreased with increasing Zr concentration. The BNKTZ-3 ceramics showed an enhanced unipolar field-induced strain of 0.43%. The dynamic piezoelectric coefficient ( d 33 * = S max/ E max) obtained for this composition was 614 pm/V, much higher than that of polycrystalline lead-free and hard Pb(Zr,Ti)O 3 ceramics. These results indicate that an appropriate amount of Zr substitution significantly enhances the field-induced strain level of BNKT ceramics and can be considered as one of promising candidate materials for lead-free electromechanical actuator applications.