Sintering of alumina by 2.45 GHz microwave heating

Sintering behavior of alumina by 2.45 GHz microwave heating was investigated on the base of an isothermal barrier structure, which consisted of an inner blanket (composed of mullite and α-alumina) and an outer one (fibrous alumina-silica board). The temperature difference within the sample was predicted from the densities of samples with different sizes, i.e. different volume to surface ratios. The temperature difference was largest at about 1500°C. The thermal stresses caused by the temperature difference did not produce microcracks in the sample. Very little temperature difference in the sample would exist at 1600°C. The homogeneous microstructures were observed by SEM in the sample sintered at 1600°C. Bending strength was measured for test pieces, which were cut from the center of sample (size before sintenng: 60 × 60 × 30 mm) sintered at 1600°C.