Raytheon Company

Kenneth J Saunders

Richard L Gentilman

Randal W Tustison

An optically transmittant body comprising a solid solution of a ternary sulfide and a selected binary sulfide such as a solid solution of calcium lanthanum sulfide and phase lanthanum sulfide is provided by precipitating out of a nitrate solution of calcium and lanthanum, a starting powder of calcium carbonate and lanthanum carbonate. The molar ratio of lanthanum to calcium is greater than 2.0 moles lanthanum to 1.0 moles of calcium nitrate. The starting powder is reacted with a sulfurizing agent such as hydrogen sulfide to convert such starting powder into a powder of the solid solution of calcium lanthanum sulfide and phase lanthanum sulfide. The precipitate ion reaction forms a homogenous fine particle size starting powder of calcium carbonate and lanthanum carbonate which is substantially and uniformly converted into the solid solution powder. The phase lanthanum sulfide has a similar crystallographic structure as the calcium lanthanum sulfide. The solid solution of calcium lanthanum sulifide and the phase lanthanum sulfide powder is then compacted into the desired form of the optically transmittant body, and is then sintered at an elevated temperature in an atmosphere of excess sulfur to increase the density of the compacted body. An atmosphere including sulfur is provided to prevent decomposition of the material and to aid in the conversion of any residual, unsulfurized calcium carbonate, lanthanum carbonate materials present in the solid solution. The sintered material is then compressed at an elevated pressure and temperature providing the material of the optically transmittant body.

Optical material and process for making the same

An optically transmittant body of a ternary sulfide material such as calcium lanthanum sulfide is provided by concurrently precipitating from a nitrate solution of calcium and lanthanum, calcium carbonate and lanthanum carbonate. The precipitation reaction forms a homogeneous fine particle size starting powder of calcium carbonate and lanthanum carbonate powders. The starting powder is reacted with a sulfurizing agent such as hydrogen sulfide to convert such starting powder into a calcium lanthanum sulfide powder. The particle size of the homogeneous starting powder is sufficiently small to permit substantially complete and uniform conversion of such starting powder into the calcium lanthanum sulfide powder. The calcium lanthanum sulfide powder is then compacted into the desired form of the optically transmittant body and is subsequently sintered at an elevated temperature in an atmosphere of excess sulfur to increase the density of the material. An excess sulfur atmosphere is provided to prevent decomposition of the calcium lanthanum sulfide and to aid in the conversion of any residual calcium carbonate, lanthanum carbonate material present in the calcium lanthanum sulfide. The sintered calcium lanthanum sulfide material is then compressed at an elevated pressure and temperature providing the material of the optically transmittant body.

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Waltham, MA, United States of America

Kenneth J Saunders