Poling effect and sintering temperature dependence on fracture strength and fatigue properties of bismuth titanate based piezoceramics

Abstract In this study, a type of high-temperature piezoceramic, Bi4Ti2.95W0.05O12.05 + 0.2 wt% Cr2O3 (BTWC), was synthesised via a solid-reaction technology and sintered at different temperatures (1050–1150 °C). A modified small punch (MSP) method was used to investigate the fracture mechanisms and fatigue behaviours of both the unpoled and poled BTWC ceramics. The results indicate that BTWC ceramics sintered at the temperature range exhibit good densification and that both the grain size and the piezoelectric constant increase with increases in the sintering temperature. The unpoled sample sintered at a higher temperature tends to exhibit higher mechanical strength and presents a mixed fracture mode of transgranular fracture and intergranular fracture. Furthermore, it exhibits a strong susceptibility to dynamic fatigue properties. However, the poling effect decreases the mechanical strength and further deteriorates the dynamic fatigue properties and cyclic fatigue behaviours due to the internal stress induced in the poling process. For the dynamic fatigue behaviour, slow crack growth due to the stress corrosion at the crack tip is considered as the dominant mechanism of fatigue damage. Furthermore, cyclic fatigue damage is mainly observed in the low cycle fatigue regime, and the corresponding failure mechanisms are attributed to the pre-existing defects and their significant sensitivity to high stress.