The effect of annealing atmospheres on the segregation behaviors in Ti-doped α-Al₂O₃ grain boundary

Abstract

The effect of different annealing atmospheres on the atomic structures and dopant segregation behaviors in Ti-doped grain boundaries (GBs) of alumina was studied by using atomic-resolution scanning transmission electron microscopy, energy dispersive X-ray spectroscopy and electron energy loss spectroscopy. In addition to the Ti dopants, Ca impurities also segregated to the GBs. It is found that the atomic structure of Ti-doped GBs is symmetric in the reducing atmosphere, while it changes into an asymmetric one with further annealing in air. The different GB structures and segregation behaviors of Ti and Ca in air may result from the partially oxidization of Ti³⁺ to Ti⁴⁺ and less oxygen vacancies when annealed in air. Our results indicate that the annealing atmosphere strongly affect GB segregation behaviors in alumina.