Phase structure regulation and enhanced Curie temperature of (K,Na)NbO3-based piezoelectric ceramics

Abstract

ABSTRACT (K,Na)NbO3 (KNN) ceramics can achieve high piezoelectric properties under the action of polymorphic phase boundary (PPB), but their application is always limited by low Curie temperature (T c). In this work, a new system of lead‐free (1-x)K0.4Na0.6Nb0.96Sb0.04O3-xLi0.5Bi0.45La0.05ZrO3 (KNNS-xLBLZ) ceramics is first designed and prepared to search for good piezoelectric properties and high Curie temperature. The crystal structure, dielectric, piezoelectric, microstructure and conductivity of the system were systematically investigated. The analysis of the dielectric temperature dependence reveals that doping Li0.5Bi0.45La0.05ZrO3 increases rhombohedral-orthorhombic phase temperature (T R-O) and decreases orthorhombic-tetragonal phase transition temperature (T O-T), and then achieves O-T phase coexistence at room temperature. In particular, a piezoelectric coefficient (d 33) of 320 pC/N and T c = 290°C are achieved at 0.02. Ceramics prepared by this ion doping and phase regulation method possess high d 33 and T c. These results show that KNNS-xLBLZ ceramics have great potential for application in high-temperature environments.