Abstract
This high‐resolution transmission electron microscopy (HRTEM) study revealed changes due to calcium segregation in the atomistic structure of the (1104) twin boundary in α‐Al2O3. Calcium grain‐boundary doped and undoped twins were prepared using ultrahigh vacuum (UHV) diffusion bonding of two highly pure single crystals. Two distinct boundary configurations—each having mirror and glide mirror symmetry—were found in the calcium‐doped bicrystal. Thus far, only the mirror‐related configuration could be identified in the undoped boundary. To estimate the atomistic structure of the grain boundary, simulated images of four supercells with different calcium contents were compared to experimental HRTEM micrographs. The amount of calcium found at the (1104) twin boundary using this method was consistent with results that were obtained by energy‐dispersive X‐ray spectroscopy.
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