Piezoelectricity of (K,Na)(Nb,Sb)O3–SrZrO3(Bi,Ag)ZrO3 piezoceramics and their application in planar-type actuators

Abstract

A Fe₂O₃–added 0.96(K_0.5Na_0.5)(Nb_0.94Sb_0.06)–0.01SrZrO₃–0.03(BiAg)ZrO₃ [KNNS–0.01SZ–0.03BAZ] piezoceramic was well densified at 1090 °C. It exhibited a large piezoelectric charge constant (d₃₃) of 650 pC/N, which is close to the largest d₃₃ value reported in the literature. This sample has a tetragonal–orthorhombic–rhombohedral (T–O–R) structure, in which each structure has a similar proportion. Moreover, nanodomains (2 nm × 15 nm) with a low domain boundary energy were found in this sample, which exhibited relaxor properties. Therefore, the presence of a T–O–R multi-structure and nanodomains is responsible for the large d₃₃ value of this sample. A KNNS–0.01SZ–0.03BAZ thick film was synthesized, and it also had a T–O–R multi-structure with a large d₃₃ (630 pC/N). A planar-type actuator was produced using this thick film, and this actuator exhibited large acceleration (335 G at 120 V mm⁻¹) and displacement (231 μm at 120 V mm⁻¹). Hence, the KNNS–0.01SZ–0.03BAZ thick film is a good candidate for lead-free piezoelectric actuators.