26 September 2003 Transparent sintered sub-μm Al2O3 with infrared transmissivity equal to sapphire
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Abstract
New grades of sintered (polycrystalline) corundum ceramics have been shown to exhibit a ballistic shielding power close to SiC/B4C composites when manufactured with a grain size of about 500 nm. It is demonstrated here that these Al2O3 ceramics become transparent when their residual porosity is decreased to less than 0.05 %. Specifically, in the IR range between about 2 and 6 μm their transmissivity equals that of sapphire approaching the upper theoretical limit for wavelengths of 2.5-4.5 μm. This opens the way to new possible applications such as IR domes. These optically and mechanically homogeneous ceramics can be manufactured with a wall thickness up to 15 mm by a wet casting approach. The technology enables the manufacture of complex hollow spheres which after sintering are transparent in visible light without polishing.
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Andreas Krell, Andreas Krell, Guenter M. Baur, Guenter M. Baur, Claus Dahne, Claus Dahne, "Transparent sintered sub-μm Al2O3 with infrared transmissivity equal to sapphire", Proc. SPIE 5078, Window and Dome Technologies VIII, (26 September 2003); doi: 10.1117/12.485770; https://doi.org/10.1117/12.485770
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