Piezoelectric properties of (Na _0.5 K _0.5 )(Nb _1‐ <scp> _x S </scp> b _x )O ₃ ‐SrTiO ₃ ceramics with tetragonal‐pseudocubic <scp>PPB</scp> structure

Abstract

Abstract CuO‐added 0.96(Na 0.5 K 0.5 )(Nb 1‐ x S b x )O 3 ‐0.04SrTiO 3 ceramics sintered at the low temperature of 960°C for 10 hours showed dense microstructures and high relative densities. The specimens with 0.0 ≤ x ≤ 0.04 had orthorhombic‐tetragonal polymorphic phase boundary ( PPB ) structure. Tetragonal‐pseudocubic PPB structure was observed in specimens with 0.05 ≤ x ≤ 0.07, while the specimen with x = 0.08 has a pseudocubic structure. The structural variation in the specimens is explained by the decreases in the orthorhombic‐tetragonal transition temperature and Curie temperature with the addition of Sb 5+ ions. The specimens with 0.05 ≤ x ≤ 0.07, which have tetragonal‐pseudocubic PPB structure, had large electric field‐induced strains of 0.14%‐0.016%. Moreover, these specimens also showed increased d 33 values between 280 pC /N and 358 pC /N. In particular, the specimen with x = 0.055 showed particularly enhanced piezoelectric properties: d 33 of 358 pC /N, k p of 0.45, and the electric field‐induced strain of 0.16% at 4.5 kV/mm.