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1 November 1997 Spinel: where did it go?
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Polycrystalline magnesium aluminum oxide, transparent from 200 nanometers to 6 microns, offers a unique combination of optical and physical properties. A superior dome and window material in respect to rain and particle erosion, solar radiation, high temperatures and humidity; it is resistant to attack by strong acids, sea water, and jet fuels. Although it had been qualified for, and designed into several advanced UV/visible/IR optical systems, production of hot-pressed Spinel was stopped at Alpha Optical Systems in 1993 by the parent company Coors Ceramics. Development efforts on cold-pressed/sinter/HIP Spinel at RCS Technologies are reportedly stalemated at the present time. Therefore, there is no known significant effort directed toward the development of polycrystalline Spinel. however, the author is in contact with both domestic and foreign laboratories which have expressed a desire to develop the technology for transparent Spinel. Renewed development may begin during calendar year 1997. Because of the apparent continuing significant interest in Spinel this paper will review the properties of Spinel and will compare the most significant properties of Spinel with sapphire and aluminum oxynitride. The limitations of competing manufacturing processes, will be mentioned. Grinding and polishing considerations will be reviewed in respect to maximizing optical and structural properties.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Donald W. Roy "Spinel: where did it go?", Proc. SPIE 3134, Optical Manufacturing and Testing II, (1 November 1997);

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