Atomic and electronic band structures of Y-doped Al2O3 grain boundaries

An Y-doped Sigma 7{4 (5) over bar 10}[0001] Al2O3 grain boundary was fabricated by the bicrystal method. The grain boundary segregation structure was studied using atomic-resolution scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. It was found that the atomic structure of the Y-doped grain boundary differs from that of the non-doped grain boundary, indicating that Y doping induced the structural transformation from asymmetrical shape to symmetrical shape in the grain boundary core. Apart from Y, impurities of Ca were also segregated at the grain boundary. Both Y3+ and Ca2+ are segregated at the same atomic columns in the grain boundary, mainly due to their larger ionic size compared with Al3+. In addition, valence electron energy loss spectroscopy measurements indicate that the bandgap energy of the doped grain boundary is about 0.5 eV smaller than that of the pristine grain boundary. (C)2022 The Ceramic Society of Japan. All rights reserved.