Characterization of acceptor-doped (Ba, Ca)TiO 3 “hard” piezoelectric ceramics for high-power applications

Abstract Acceptor Mn or Co-doped Ba 0.925 Ca 0.075 TiO 3 (abbreviated as BCT-Mn and BCT-Co) lead-free piezoelectric ceramics with high density and fine grains were synthesized by conventional solid-state reaction method. The phase structure and electrical properties of the ceramics were investigated. The acceptor-doped BCT ceramics were found to exhibit asymmetrical polarization-electric field hysteresis loops corresponding to the presence of an internal bias field E i , indicating that the domain walls were pinned by preferentially oriented defect dipoles formed by the acceptors and oxygen vacancies. High mechanical quality factor Q m and low dielectric loss tanδ were obtained for the ceramics due to the strong internal bias field ( E i =4–5kV/cm). In particular, BCT-Mn ceramics exhibited the best properties, with mechanical quality factor Q m =1020, dielectric loss tanδ= 0.2% and piezoelectric coefficient d 33 =190 pC/N. Furthermore, the planar electromechanical coupling factor k p for BCT-Mn ceramics was found to be larger than 0.4 in the temperature range of 25 °C to 75 °C. These results indicate that the Mn-doped BCT lead-free ceramics material is a promising candidate for high-power piezoelectric applications.