Atomic-scale segregation behavior of Pr at a ZnO [0001] Sigma 49 tilt grain boundary

The atomic arrangement and segregation of Pr dopants at a ZnO [0001] Sigma 49 grain boundary were investigated by Z-contrast scanning transmission electron microscopy and first-principles calculations. Scanning transmission electron microscopy revealed that Pr selectively segregated at three kinds of the grain boundary atomic sites. It was found that atomic arrangement of the Pr-doped ZnO [0001] Sigma 49 grain boundary was similar to that of the undoped GB, and Pr substituted at three kinds of Zn sites at the grain boundary. Comparison of the experimental image with the structure of the undoped grain boundary revealed that the Zn-O interatomic distances are the longest at these Zn sites. There was a tendency for lengths and electronic structures of Pr-O bonds at the Pr-doped ZnO Sigma 49 grain boundary, when compared with those in the Pr-doped ZnO crystal bulk, to be closer to those in the stable Pr(2)O(3) crystal phases.