Method for producing transparent polycrystalline body with high ultraviolet transmittance

A process for producing a sintered polycrystalline body consisting essentially of magnesia-alumina spinel wherein said body has an in-line transmittance per 1.88 mm thickness in all wavelengths in wavelength range of from about 0.2 microns to about 0.4 microns of not less than the transmittance shown by line A in FIG. 2, comprising:

• providing a powder consisting essentially of magnesia-alumina spinel, said magnesia-alumina spinel powder comprising less than about 50 ppm of oxides selected from the group consisting of oxides of chromium, copper, iron, gallium, manganese, lead, titanium, vanadium, and zinc, and combinations thereof;
• producing a closed porosity body from said powder;
• and
• hot isostatic pressing said closed porosity body at an elevated temperature of at least about 1400.degree. C. and at a pressure of at least about 20,000 psi for a time effective to produce a sintered body having a porosity less than about 0.001 volume percent.

A sintered polycrystalline body consisting essentially of magnesia-alumina spinel wherein said body has an in-line transmittance per 1.88 mm thickness in all wavelengths in the wavelength range from about 0.2 microns to about 0.4 microns of not less than the transmittance shown by Line B in FIG. 2 produced by a process comprising:

• producing a powder comprising magnesia-alumina spinel, said magnesia-alumina spinel powder comprising less than about 50 ppm of oxides selected from the group consisting of oxides of chromium, copper, iron, gallium, manganese, lead, titanium, vanadium, and zinc, and combinations thereof;
• producing a closed porosity body from said powder;
• and
• hot isostatic pressing said closed porosity body at a temperature of at least about 1400.degree. C. and at a pressure of at least about 20,000 psi to reduce residual porosity.