Grain-boundary structural transformation induced by geometry and chemistry

Since the presence of dopant at grain boundaries (GBs) has a big impact on physical properties of crystalline solids, GB atomic structure and dopant location have been clarified in detail in some particular cases. However, further studies are required to reveal the underlying structure-formation mechanisms, because there are huge numbers of possible structures due to a wide variety in GB geometry, such as crystallographic orientation relationships and GB planes. Although an ultimate goal of the GB-structure study is to understand all GBs with different geometries, it is quite unrealistic to investigate large numbers of GBs on the atomic scale. Alternatively, a realistic and important step toward this goal is to clarify a GB structure-geometry-chemistry relationship. In this Brief Report we report that change of GB geometry together with doping of praseodymium induces structural transformation in a zinc oxide GB. This demonstrates that geometrical and chemical effects cooperatively play a crucial role in determining the GB atomic-scale structure.