General Electric Company

Chester R O'Clair

Charles D Greskovich

Svante Prochazka

William Paul Minnear

Robert J Riedner

Erdogan O Gurmen

Transparent, polycrystalline garnet bodies having desirable properties for use as laser material, luminescent x-ray scintillator materials and other uses are produced by mixing a chloride source solution of the desired cations with a basic ammonium solution to produce a precipitate having a substantially uniform composition which can be further processed to provide the desired transparent body. This precipitate is separated from the solution, dried, thermally decomposed at a temperature in the range from 700.degree. to 1,000.degree. C., pressed to form a compact, isostatically pressed at up to 60,000 psi to provide a green, unsintered compact having a density in the vicinity of 55% of theoretic density. That green compact is then sintered in oxygen at a temperature between 1,400.degree. and 1,700.degree. C. to produce the desired transparent body. Alternatively, the compact may be sintered in oxygen at temperatures in the range from about 1,400.degree. to about 1,600.degree. C. to a closed pore stage and then hot isostatically pressed at high pressure to provide the desired transparent body.

Transparent polycrystalline garnets

A polycrystalline body having a composition comprised of Y.sub.2-x Sr.sub.x O.sub.3-x/2 wherein x ranges from about 0.0015 to about 0.012.

Strontium-containing yttrium oxide ceramic body

A sinterable yttrium oxide powder is produced useful for pressureless sintering a compact thereof into an optically translucent or transparent body. The yttrium oxide powder has a specified particle size range and specific surface area. It is formed by preparing yttrium oxalate hydrate powder by means of the wet chemical oxalate method, comminuting the yttrium oxalate hydrate powder to a required degree and calcining the yttrium oxalate hydrate.

Yttrium oxide ceramic body

A dense polycrystalline silicon nitride body is produced by hot-pressing a particulate mixture of silicon nitride and a beryllium additive.

Hot pressing of silicon nitride using beryllium additive

A dense polycrystalline silicon nitride body is produced by hot-pressing a particulate mixture of silicon nitride and a magnesium silicide additive.

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Latham, NY, United States of America

Chester R O'Clair