Improving piezoelectric properties by controlling phase structure and crystal orientation

Abstract

In this study, 〈001〉-textured (1 − x)K_0.48Na_0.52Nb_0.96Sb_0.04O₃-xBi_0.50(K_0.48Na_0.52)_0.50Zr_0.50Hf_0.50O₃ [abbreviated as (1 − x)KNNS-xBKNZH, x = 0.01–0.04] lead-free ceramics were prepared by templated grain growth (TGG) method and sintered by a two-step process. Excellent longitudinal piezoelectric coefficient d₃₃ (434 pC N⁻¹) and piezoelectric strain coefficient (722.5 pm V⁻¹) are achieved in the textured 0.97KNNS-0.03BKNZH ceramics. The excellent piezoelectric properties can be ascribed to both the coexisting R–O–T multiphases and the 〈001〉 crystal orientation. In addition, a high electromechanical coupling coefficient k_p (∼73.6%) is attained in textured ceramics with x = 0.02. The values of d₃₃ and k_p also display high thermal stability (with rate of change < ±10%) over 25–120 °C in textured ceramics with x = 0.03 and 0.04. Excellent comprehensive properties suggest that 〈001〉-textured (1 − x)KNNS-xBKNZH ceramics are promising lead-free candidates for actuator and transducer applications.