Improving electrical properties and toughening of PZT-based piezoelectric ceramics for high-power applications via doping rare-earth oxides

Ceramics show brittle nature because of ionic and covalent bondings. However, the need for reliable high-power applications with vibrational displacements under high electric fields and stress loadings demands robust piezoelectric ceramics. In this work, three series of Lead Zirconium Titanate-based piezoelectric ceramics for high-power applications are synthesized via solid solution reaction technique. The microstructures and phases are manipulated by doping different rare-earth oxides Nd2O3, Dy2O3 and Yb2O3. Although all as-sintered piezoelectric ceramics show a perovskite structure with a coexistence of rhombohedral and tetragonal phases, phase fraction, grain size distribution and attendant electrical and mechanical properties vary depending on the doping species and contents. The comprehensive properties of optimized piezoelectric ceramics for high-power applications are: d33 = 292–308 pC/N, kp = 54.2–57.0%, Qm = 320–400, ε33T/ε0 = 1140–1210 and KIC = 1.55–1.60 MPa m1/2. These properties are improved by 19.0%–27.0% compared to the original composition without doping. The toughening mechanism by doping rare-earth oxides is discussed. Nd3+, Dy3+ and Yb3+ substitution and compensation at A-sites of perovskite unit cells generate extrinsic vacancies besides the intrinsic vacancies caused due to PbO evaporation during sintering, which make the domain wall highly mobile and result in softened ferroelectrics. Our results show an efficient route to toughen the PZT-based piezoelectric ceramics and enhance electrical properties synergistically via doping appropriate amounts of rare-earth oxides.