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

In this work, (K 0.48 Na 0.52 )NbO 3 −0.05Ca x (Bi 0.5 Na 0.5 ) 1− x ZrO 3 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 orthorhombic-tetragonal 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 ∼308 pC/N and k p ∼49.0%, together with a high Curie temperature of T C ∼328 °C. Therefore, the material system of this work is a promising candidate for piezoelectric applications.