Tailoring hardness behaviors of BIT-based piezoceramics via doping and annealing strategies

Bismuth titanate (BIT) piezoelectric ceramics are perceived as a strong competitor in high temperature appli-cations. Currently, a mass of work has been done to optimize the electrical performance of the ceramic utilizing different strategies. However, little attention has been paid to the mechanical behaviors of BIT ceramics, espe-cially the research on mechanical hardness behaviors under doping and annealing, limiting the deep under-standing for ceramics and its further development of practical applications. In this work, the mechanical hardness behaviors of a type of bismuth titanate-based ceramics [Bi3.96Ce0.04Ti3-xWxNbxO12 (BCTWN)] at different doping contents and selectively annealing temperatures were investigated using nanoindentation and Vickers indentation techniques. The results show that the hardness is strongly dependent doping contents, wherein the samples with smaller grain size and higher density exhibit bigger hardness. For the poled samples, a higher annealing temperature could restore more domain walls and induce more oxygen vacancies in the samples, along with higher elastic recovery and less remanent strain, shedding extra deformation resistance to make sample harder. Moreover, a schematic of defect assistant domain wall pinning mechanism is proposed to further rationalize the enhanced deformation resistance by annealing strategy. This work helps us deep under-stand the deformation mechanism of BIT ceramics beneath indentation, and provides insight into tailoring mechanical hardness behaviors via doping and annealing strategies.