Phase structure, microstructure, and piezoelectric properties of potassium-sodium niobate-based lead-free ceramics modified by Ca

In this work, (K0.48Na0.52) NbO3-0.05Ca(x)(Bi0.5Na0.5)(1-x)ZrO3 lead-free piezoelectric ceramics were prepared by a conventional solid-state sintering method. The effects of Ca content on their phase structure, microstructures, and piezoelectric properties were systematically studied. With the increasing of Ca content, the rhombohedral-orthorhombic phase temperature gradually increases and Curie temperature of the ceramics without a conspicuous change. In addition, appropriate Ca ( x <= 0.2) content promotes the grain growth, which leads to a denser microstructure. Rhombohedral-orthorhombic and orthorhombictetragonal phase coexistence has been obtained in the composition range of 0.15 <= x <= 0.3. The ceramics with x = 0.2 possess enhanced piezoelectric properties of d(33)similar to 308 pC/N and kp similar to 49.0%, together with a high Curie temperature of TC similar to 328 degrees C. Therefore, the material system of this work is a promising candidate for piezoelectric applications. (C) 2016 Elsevier B.V. All rights reserved.