This was a ferroelectric material having a rhombohedral R3c structure at room temperature. A LiNbO3 bicrystal with a }/<10•0> 1° low-angle tilt grain boundary was successfully fabricated by diffusion bonding. The resultant boundary was then investigated using high-resolution TEM. The boundary comprised a periodic array of dislocations with >. They dissociated into two partial dislocations by climb. Crystallographic considerations suggested that the Burgers vectors of the partial dislocations should be •and •, and a stacking fault on } was formed between the two partial dislocations. From the separation distance of a partial dislocation pair, the stacking-fault energy on } was estimated to be 0.25J/m2 on the basis of isotropic elasticity theory. Dislocation Structure at a {1210}/<1010> Low-Angle Tilt Grain Boundary in LiNbO3. A.Nakamura, E.Tochigi, J.Nakamura, I.Kishida, Y.Yokogawa: Journal of Materials Science, 2012, 47[13], 5086-96