Twin boundary modification induced by dopant segregation

Revealing the interaction between dopants and grain boundaries (GBs) is crucial for tailoring the material properties by elemental doping. It is generally believed that the segregation behavior of dopants depends on the initial structure of pristine GBs and the effect of GB segregation is localized since the dopants only affect the arrangement of neighboring atoms. In this study, aberration-corrected transmission electron microscopy observations reveal that pristine α-Fe 2 O 3 possesses three types of (0001) coherent twin boundaries (TBs) with different displacement vectors, which evolve into the same TB after co-doping of Sr and Si. The dopant co-segregation at the TBs causes the localized TB structural transition of Fe 2 O 3 grains, which consequently fundamentally alters the local atomic coordination and the relative alignment of the adjacent grains. First-principles calculations suggest that the spontaneous segregation of large-sized Sr atoms induces a local interfacial modification and promotes the segregation of Si atoms. These findings suggest that dopants can not only completely modify the structure of GBs but also induce collective atomic rearrangements across the interface, thereby providing insights for atomic-scale interfacial engineering.