Role of oxygen‐vacancy in piezoelectric properties and fatigue behavior of (Bi0.5Na0.5)0.93Ba0.07Ti1+xO3 ceramics

In this reported study, (Bi0.5Na0.5)0.93Ba0.07Ti1+xO3 (abbreviated as BNBT1+x) ceramics, containing Ti‐nonstoichiometry that ranged from a 2% deficiency to a 1% excess, were designed and systematically characterized. The results of the X‐ray diffraction Rietveld refinement and X‐ray photoelectron spectroscopy analysis of these materials revealed that the amount of Ti in the BNBT1+x ceramics significantly affected the degree of coexistent rhombohedral/tetragonal phases and also affected the content of singly/doubly charged oxygen‐vacancy (VO·/VO··) in the ceramics. After poling and 105 fatigue cycles, the variation in Raman resonance line‐width of the Ti–O bond in the BNBT1+x ceramics was found to be strongly dependent on the amount of Ti in the ceramic. The TiTi4+(3+)′-VO·→TiTi4+(3+)′-VO·· transformation and clustering of the TiTi4+(3+)′-VO·· defects under electrical loading were considered to be a critical factor in electric field‐induced structural transition and fatigue properties of the material. Although high TF‐R/Td of ~160 oC was detected in BNBT1+x ceramics with whether Ti excess or high Ti deficiency, high electric conductivity with ~1 eV and significant degradation in Smax and d33*max after 105 electrical loading were found, probable due to large amounts of incipient defects.