alumina bicrystals were fabricated by a hot joining technique at 1500 deg C in air to obtain ten kinds of [0001] symmetric tilt grain boundaries which included small angle, CSL and high angle grain boundaries. Their grain boundary structures were investigated by high-resolution electron microscopy (HREM), and the respoective grain boundary energies were systematically measured by a thermal grooving technique. It was found that grain boundary energy strongly depended on the grain boundary characters, e.g., there were large energy cusps at low sum CSL grain boundaries. But, main part of grain boundary energy is likely to be due to the strain energy around the grain boundary, and he contribution of atomic configuration is not sl large. Small angle grain boundaries were consisted of an array of partial dislocation with Burgers vector of 1/3[1100] to form the stacking faults between the dislocations. The behavior of grain boundary sliding was also investigated for typical grain boundaries by high-temperature creep test at 1400 deg C. As the result, the occurrence of grain boundary sliding was found to depend on the grain boundary atomic structure.
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