Unraveling the influence of oxygen vacancies on sintering behavior and microstructure evolution in perovskite BaTiO3 ceramics
Wenjie Liu, Xinlei Pan, Yibin Jiang, Guoqiang Wu, Juanjuan Xing, Hong-Qiang Fan, Jianfeng Hu
Abstract
Oxygen vacancies, as one of the fundamental and intrinsic defects pervasive in metal oxides, play crucial roles in tuning their physicochemical properties. However, it remains elusive how oxygen vacancies fundamentally influence the thermal stability of nanograined oxide, the correlative sintering processes, and the microstructural formation of polycrystalline nanograined materials. Here, the effects of oxygen vacancies on the sintering behaviors (involved with densification and grain growth) of perovskite BaTiO 3 nanocrystals are investigated by tuning the concentration of oxygen vacancies. Surprisingly, small differences in the concentration of oxygen vacancies in nanocrystals are revealed to result in significant differences in sintering behaviors and the resulting microstructures. Counterintuitively, BaTiO 3 nanocrystals with higher concentrations of oxygen vacancies exhibit lower growth rates than those with lower concentrations of oxygen vacancies. Furthermore, a recently developed grain growth theory can well explain the changes in grain growth behavior due to varying concentrations of oxygen vacancies, as well as reveal the correlation between grain growth and densification. In addition, the observed differences in the concentration of oxygen vacancies result in distinctly different twinning microstructures in perovskite BaTiO 3 ceramics. These findings have important implications for the sintering of the non-stoichiometric compounds.