US 4,765,931 A · Optical material and process for making the same

Abstract

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.

Claims19

Dependent claims

A method of forming an optically transmissive body comprising a binary sulfide and a ternary sulfide said ternary sulfide having two cation types, a first one selected from the group consisting of metal cations, a second one selected fro the group consisting of the lanthanum series cations comprising the steps of:

reacting the two cation types with a material which when reacted provides a source of sulfide anions to convert all of said first cation type and a first portion of said second cation type into the ternary sulfide, and reacting a second remaining portion of said second cation type into the binary sulfide, said binary sulfide forming a solid solution with said ternary sulfide with said metal cations and lanthanum series cations selected from those which will form a binary sulfide ternary sulfide solution;
and
forming the binary sulfide and ternary sulfide into the optically transmissive body.

A method of forming an optically transmissive body comprising a solid solution of a calcium lanthanum sulfide and lanthanum sulfide comprising the steps of:

forming a starting powder including calcium and lanthanum cations in the ratio of greater than 2.0 moles of lanthanum to 1.0 moles of calcium;
reacting at an elevated temperature of at least 900.degree. C. the starting powder with a material which when reacted provides a source of sulfide anions to convert a first portion of the lanthanum cations and all the calcium cations into calcium lanthanum sulfide, and the remaining portion of lanthanum cations into the lanthanum sulfide forming a solid solution with said calcium lanthanum sulfide;
and
processing the solid solution of calcium lanthanum sulfide and lanthanum sulfide into the optically transmissive body.

1 more element

Dependencies are inferred from the claim text.

Optical material and process for making the same

Life of this patent

Optical material and process for making the same

Life of this patent

Abstract

Claims19