Spark plasma sintering of high-TC calcium bismuth niobate (CaBi2Nb2O9) with superior piezoelectric performance

Calcium bismuth niobate (CaBi2Nb2O9) is a promising ceramic material for high-temperature piezoelectric applications due to its high Curie temperature (TC) of 940 degrees C. However, its practical use is limited by poor piezoelectric performance and low direct-current (DC) electrical resistivity at elevated temperatures. In this study, we introduced pseudo-tetragonal distortion into CaBi2Nb2O9 by substituting rare-earth thulium ions, which reduced domain wall energy, facilitated domain switching, and decreased the presence of oxygen vacancies. These enhancements significantly improved both the piezoelectric performance and DC electrical resistivity of the material. To further enhance piezoelectric performance, we prepared textured thulium-substituted CaBi2Nb2O9 ceramics with a Lotgering factor (f) of up to 77.4 % using a two-step spark plasma sintering method. The resulting textured CaBi2Nb2O9 ceramics exhibited superior piezoelectric performance, with a piezoelectric constant d33 of 25.2 pC/N, four times higher than that of non-textured CaBi2Nb2O9. Importantly, these textured ceramics maintained excellent electrical properties at elevated temperatures, suggesting their suitability for hightemperature piezoelectric device applications.