Enhanced piezoelectric properties of (1-x)(K0.5,Na0.5)(Nb0.97Sb0.03)O3-x (Bi0.5Ca0.5)ZrO3 ceramics through the establishment of polymorphic phase boundary

(1-x)(K-0.5,Na-0.5)(Nb0.97Sb0.03)O-3-x(Bi0.5Ca0.5)ZrO3 [(1-x)KNNS-xBCZ] lead free piezoelectric ceramics with excellent electrical properties were successfully fabricated through the conventional solid-state reaction method. The relationship between (Bi0.5Ca0.5)ZrO3 content and their phase structure, microstructure, piezoelectric properties, dielectric properties and ferroelectric properties were systematically studied. The results show that the unmodified KNN-based ceramics are orthorhombic phase and tetragonal phase appears after the introduction of BCZ and demonstrate that the O-T polymorphic phase boundary (PPB) was formed in 0.01 <= x <= 0.04. Benefiting from the construction of the PPB, a large piezoelectric coefficient (d(33) similar to 303 pC/N), dielectric constant (epsilon(r) similar to 7158) and a high Curie temperature (T-C similar to 340 degrees C) were achieved in the ceramics with x = 0.02. The coexistence of O-T phases promotes the motion of domain walls, which is the fundamental reason for the improvement of piezoelectric properties. The ceramics demonstrated remarkable piezoelectric properties and high Curie temperature (T-C similar to 340 degrees C), which are promising candidates for practical application to eliminate the Pb-based piezoelectric ceramics from the market. (C) 2021 Elsevier B.V. All rights reserved.