Fig. 10 shows the SEM micrographs of the gained a-Al2O3 powders from precursors with different amounts of a-Al2O3 seed. From the XRD analysis, we know that the pure a-Al2O3 can be obtained from Al-3 until the calcination temperature reached to 1100 C. However, the pure a-Al2O3 from Al-7, Al-8 can be gained at 1000 C. The a-Al2O3 from Al-3 (Fig. 10a) has relatively larger grains with seriously hard aggregation than the a-Al2O3 powders with various amount of additives (Fig. 10b–d). Fig. 11 shows the TEM micrographs of a-Al2O3 from different precursors. The Al2O3 from Al-3 had two kinds of particle size, which was caused by