Atomic and electronic structures of natural and artificial rutile TiO2 grain boundaries

Grain boundaries (GBs) significantly influence the properties and applications of materials. Due to the advantages associated with GB design and structural characterization, artificial bicrystal GBs are frequently constructed as model samples to mimic the atomic structures and properties of naturally occurring GBs in materials. The question of whether artificial and natural GBs exhibit identical structures and properties has been a long-debated scientific issue. In this study, we fabricated artificial bicrystal (011) and (031) twin boundaries (TBs) in rutile TiO2 (R-TiO2) through solid-state diffusion bonding, while their natural counterparts were obtained from an R-TiO2 thin film prepared via pulsed laser deposition. We systematically investigated the atomic and electronic structures of both artificial and natural (011) and (031) TBs using aberration-corrected scanning transmission electron microscopy integrated with electron energy loss spectroscopy. The results demonstrated that the artificial bicrystal TBs possess precisely the same atomic and electronic structures as their natural counterparts. This study underscores that artificial bicrystal GBs serve as excellent model samples for investigating GBs.