Physical and chemical properties of crystalline materials are strongly dependent on the atomic structure of grain boundaries. Accordingly, it is essential to investigate the grain boundary structure for understanding the properties. In this study, we focused on structure of dislocations at (0001)/[112^^-0] low-angle tilt grain boundaries in lithium niobate (LiNbO_3). The core structures of the boundary dislocations were observed by scanning transmission electron microscopy (STEM) and electric property along the dislocations were investigated. It was found out by the STEM observation that the (0001)/[112^^-0] low-angle tilt grain oundary consists of the three types of dislocations. This is probably because Burgers vector of [0001] perfect dislocation is too large to form. In addition, it was confirmed that all the three boundary dislocations dissociate into two partial dislocations with a stacking fault in between. The electrical conductivity measurement showed that a part of fabricated low-angle tilt grain boundaries developed electric conductivity although it is an insulator.
