Balanced Development of Piezoelectricity and Curie Temperature in KNN-BC-xBNH Lead-Free Ceramics

Abstract

In this work, (0.996 − x)(K0.48Na0.52)NbO3-0.004BiCoO3-xBi0.5Na0.5HfO3 (abbreviated as KNN-BC-xBNH) lead-free ceramics were prepared by the conventional solid-state sintering method. The effects of Bi0.5Na0.5HfO3 content on the microstructure and piezoelectric properties of ceramic crystals were systematically studied. The results of x-ray diffraction (XRD) and temperature dependence of the dielectric constant showed that with the increase of Bi0.5Na0.5HfO3 content, the rhombohedral–orthorhombic (TR–O) and orthorhombic–tetragonal (TO–T) phase-transition temperature gradually moved to the vicinity of room temperature. The KNN-BC-xBNH lead-free ceramics with x = 0.035 exhibited optimal electrical properties of d33 ∼ 272 pC/N, kp ∼ 0.47, Pr ∼ 25.63 μC/cm2, EC ∼ 13.31 kV/cm, Curie temperature Tc ∼ 333°C, Smax ∼ 0.15% and d33* ∼ 358 pm/V. These results suggest that the KNN-BC-0.035BNH ceramic is a promising ceramic system for industrial application.