Transparent Sintered Corundum with High Hardness and Strength

Abstract

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 Al 2 O 3 ceramics having grain sizes of 0.4–0.6 μm at relative densities of >99.9%. High macrohardness (HV10 = 20–21 GPa) and four‐point bending strength (600–700 MPa; 750–900 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 >1100°C using dopants that shift the sintering temperature to high values without additional grain growth.