Coexistence of two different atomic structures in the Σ13 pyramidal twin boundary in α-Al2O3

An α-Al2O3 bicrystal with a (101¯4)/[12¯10] Σ13 grain boundary was fabricated by joining two pieces of single crystal at 1500°C in an Ar–H2 mixture gas. The resultant grain boundary was characterised by scanning transmission electron microscopy (STEM) at the atomic level. STEM observations revealed that the grain boundary consists of two regions with different atomic structures. These two structures were identified to be the most and second-most...