Giant piezoelectricity of (K,Na)(Nb,Sb)O3–(Bi,Na,K,Pb)ZrO3 ceramics with rhombohedral–tetragonal (R-T) phase boundary

(1−x)K0.42Na0.58Nb0.95Sb0.05O3–x[Bi0.5(Na0.82K0.18)0.5]0.95Pb0.05ZrO3 ceramics with rhombohedral–tetragonal phase boundary were designed to attain a giant piezoelectricity. Adding a low Pb content results in the dense microstructure, and the Pb element has been homogeneously distributed. The R–T phase boundary was formed in the ceramics with 0.035 < x ⩽ 0.045. In addition, an improved d33 of the ceramics with x = 0.04 was observed after second poling. Enhanced dielectric and piezoelectric properties of εr ∼ 2900, tan δ ∼ 0.022, d33 ∼ 460 pC/N, and kp ∼ 0.46 were observed in the ceramic with x = 0.04.