Al2O3 bicrystals containing [0 10 0 1] symmetric tilt Sigma7 grain boundaries with different grain boundary planes of 14 5 101 and (2 101 were fabricated by diffusion bonding, and the grain boundary structures were investigated by high-resolution transmission electron microscopy (HRTEM). From HRTEM observations combined with atomistic simulations, it was found that the grain boundaries exhibited characteristic atomic arrangements, and the Sigma7/{2 3 1 0} boundary contained large open spaces at its core. In compressive creep experiments for the bicrystals, these boundaries showed quite different creep behavior, although they have the same Sigma value. The measured sliding rate of Sigma7/{2 3 1 0} was much larger than that of Z7/{4 5 1 0}, which may be due to the open core structure formed in Sigma7/{2 3 1 0}. (C) 2004 Elsevier B.V. All rights reserved.