One-step sintering enabled structural stability and defect suppression even in Fe-off-stoichiometric BiFeO_(3)—BaTiO_(3)piezoceramicsOA

BiFeO_(3)—BaTiO_(3)lead-free piezoelectric ceramics exhibit superior piezoelectric properties while preser-ving a high Curie temperature.However,given the inherent Gibbs free energy law of BiFeO_(3),the system is difficult to avoid heterogeneous phases such as Bi_(25)FeO_(39)and/or Bi_(2)Fe_(4)O_(9),which are accompanied by the volatilization of Bi^(3+)and the change of Fe^(3+),resulting in low insulating properties and high dielectric loss.These factors hinder the enhancement of polarizability and the overall performance at elevated temperatures and electric field conditions.The present study focuses on a highly leaky 0.75BiFeO_(3)–0.25BaTiO_(3)ceramic,in which the Fe content is deliberately designed to be both severely excessive and deficient,and is prepared using a one-step low-temperature sintering process.It is noteworthy that the structural stability and defect suppression,even in this challenging system,are achieved via the one-step low-temperature sintering.This samples exhibit a distinctive self-tuning property and an excellent stability over a wide compositional range.First-principles density func-tional theory calculations and XPS analysis have for the first time confirmed that suppressing oxygen vacancies and Fe^(3+)valence states can reduce the concentration and mobility of hole carriers,thereby effectively reducing leakage current,with the mechanism shifting from ohmic conduction to space-charge-limited conduction.Even under the extreme compositional conditions of x=±5 and a low sintering temperature,the piezoelectric coefficients d33 reach 132 pC/N and 110 pC/N,respectively.These are significantly higher than those of the most stoichiometric 0.75BiFeO_(3)–0.25BaTiO_(3)counter-parts,setting a new performance record.