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

A Fe2O3–added 0.96(K0.5Na0.5)(Nb0.94Sb0.06)–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.