Abstract: A method for producing a transparent polycrystalline magnesia-alumina spinel body having high ultraviolet transmissivity and high strength and hardness characteristics is provided. A closed porosity body is formed from a spinel powder preferably having at least minimum purity characteristics. The closed porosity body can be formed by techniques including hot pressing and pressureless sintering. The closed porosity body is subjected to a hot isostatic pressure treatment to reduce residual porosity. The resulting body has high transmissivity of electro-magnetic radiation in the range between about 0.2 microns and about 6 microns and is resistant to abrasion or erosion, has high strength, and does not substantially deteriorate after exposure to ultraviolet light.

Abstract: A metallized spinel material and a method for producing a metallized spinel material are provided. The spinel is a high-transmissive material and, particularly, has high transmission in the ultraviolet and, preferably, the visible infrared wavelength regions as well. The high-transmissivity spinel material is metallized by applying the slurry containing a metal, such as tungsten, molybdenum and/or manganese to the substrate, and firing at en elevated temperature such as 1200.degree. to 1800.degree. C., preferably 1500.degree. to 1800.degree. C. for about 1/2 hour in a non-oxidizing atmosphere.

Abstract: A transparent polycrystalline body having high ultraviolet transmissivity is provided. The body is preferably a sintered magnesia-alumina spinel body having a transmittance of at least 85 percent in the wavelength range from 0.3 microns to 0.8 microns and a transmittance at some wavelength in the wave length range between about 0.2 and about 0.4 microns of at least about 86 percent and a porosity of less than about 0.001 percent. The sintered body is produced by a two-step method comprising forming a closed porosity body from a spinel powder and subjecting the closed porosity body to a hot isostatic pressure treatment. The resulting body has high transmissivity of electromagnetic radiation in the range between about 0.2 microns and about 6 microns, is resistant to abrasion or erosion, does not substantially deteriorate after exposure to ultraviolet light, and has high strength.

Abstract: A transparent polycrystalline body having high ultraviolet transmissivity is provided. The body is preferably a sintered magnesia-alumina spinel body having a transmittance of at least 85 percent in the wavelength range from 0.4 microns to 0.8 microns and a transmittance at some wavelength in the wavelength range between about 0.2 and about 0.4 microns of at least about 86 percent and a porosity of less than about 0.001 percent. The sintered body is produced by a two-step method comprising forming a closed porosity body from a spinel powder and subjecting the closed porosity body to a hot isostatic pressure treatment. The resulting body has high transmissivity of electromagnetic radiation in the range between about 0.2 microns and about 6 microns, is resistant to abrasion or erosion, does not substantially deteriorate after exposure to ultraviolet light, and has high strength. A number of applications of the magnesia-alumina spinel body are disclosed for which the material is advantageous.

Abstract: A dome and window for missiles and launch tubes is provided having high ultraviolet transmittance and high strength properties. The domes and windows have, in their uncoated state, and with a thickness of about 1.88 mm, a transmittance greater than about 80%, preferably greater than about 82%, and more preferably greater than about 85%, at a wavelength of 0.4 microns to 0.5 microns. The domes and windows preferably have a transmittance per 1.88 mm thickness at all wavelengths in the wavelength range between 3.0 microns and 4.0 microns of at least about 81%. The domes and windows have a flexural strength of at least about 20,000 psi and a knoop hardness of at least about 1350 kg mm.sup.-2. The domes and windows are formed of a transparent, sintered polycrystalline magnesia-alumina spinel.