Abstract
Acceptor-doped ferroelectrics generally show a pronounced aging effect. However, the KF-flux-grown BaTiO3 single crystals, which are known to contain acceptor impurities K+, show no aging effect. There has been no explanation for this exception. To solve this puzzle, we compared the ferroelectric and dielectric aging effect of as-grown and annealed KF-flux-grown BaTiO3 single crystals, and found the as-grown BaTiO3 showed almost no aging behavior, but the annealed BaTiO3 showed clear aging effect. Chemical analysis revealed that such a difference is related to their difference in composition: the as-grown crystals contain not only acceptor impurity K+, but also higher concentration of anion donor F-; on the other hand, the annealed crystals contains mostly K+ as a result of F- evaporation. Based on a defect chemistry analysis and the microscopic mechanism of the aging, the aging behavior of the two kinds of crystal can be fully explained. Our result suggests that oxygen vacancy, rather than acceptor dopant, is the crucial factor determining whether or not aging exists.
