Phase boundary design and high piezoelectric activity in (1−x)(Ba0.93Ca0.07)TiO3-xBa(Sn1−yHfy)O3 lead-free ceramics

The (1−x)(Ba0.93Ca0.07)TiO3-xBa(Sn1−yHfy)O3 (BCTSH-x-y) lead-free ceramics were synthesised by the conventional solid-state reaction method, and the influences of doping elements (Ca, Sn, Hf) content on their phase structure, microstructure, and electrical properties were systematically investigated. The phase boundaries concerning the orthorhombic and tetragonal (O-T) phases were found in the 0.925(Ba0.93Ca0.07)TiO3-0.075Ba(Sn1-yHfy)O3 ceramics with 0 ≤ y ≤ 0.25, and then the enhanced piezoelectric properties with d33 ∼ 550 pC N−1 were obtained. In addition, the addition of Hf can also improve the Curie temperature (TC) and ferroelectric properties of the ceramics. As a result, the electrical properties of BaTiO3 can be optimized by the construction of phase boundaries through Ca, Sn, and Hf co-doping.