Transparent sintered corundum with high hardness and strength

Commercial corundum powder and a liquid-shaping approach are used for manufacturing complex hollow components and large flat windows of sintered and hot isostatically pressed Al2O3 ceramics having grain sizes of 0.4-0.6 mum at relative densities of >99.9%. High macrohardness (HV10 = 20-21 GPa) and four-point bending strength (600-700 MPa; 750900 MPa in three-point bending) are associated with a real in-line transmission of 55%-65% through polished plates. The submicrometer microstructure and the optical properties can be retained for use at >1100degreesC using dopants that shift the sintering temperature to high values Without additional grain growth.