HRTEM study on grain boundary atomic structures related to the sliding behavior in alumina bicrystals

Al2O3 bicrystals containing [0 0 0 1] symmetric tilt Σ7 grain boundaries with different grain boundary planes of {4 5¯ 1 0} and {2 3¯ 1 0} 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 Σ7/{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 Σ value. The measured sliding rate of Σ7/{2 3¯ 1 0} was much larger than that of Σ7/{4 5¯ 1 0}, which may be due to the open core structure formed in Σ7/{2 3¯ 1 0}.