Infrared window materials and their fabrication
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsDaniel L. Chess, William B. White
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Abstract
Process for making densified ternary sulfide ceramics as infrared window erials using sulfide compounds MLn.sub.2 S.sub.4 belonging to the Th.sub.3 P.sub.4, CaFe.sub.2 O.sub.4 and spinel structure types. These refractory sulfides show good sinterability especially when fired in flowing hydrogen sulfide, and they can be densified by a combination of hot-pressing and hot-isostatic pressing into ceramic pieces approaching their theoretical density with closed pores and which have good transmission characteristics in the infrared region.
Claims12
Densified ternary alkaline earth-rare earth sulfides having relatively low porosity and density equal to the theoretical density thereof for infrared windows represented by a formula:
- MLn.sub.2 S.sub.4
- wherein M, Ln and S are a member of the group consisting of Ba.sup.+2, Sr.sup.+2 and Ca.sup.+2, light lanthanide ion and sulfide ion respectively.
A process for densifying to the theoretical limit ternary alkaline earth-rare earth sulfides represented by MLn.sub.2 S.sub.4, wherein M, Ln and S representing alkaline earth, light lanthanide and sulfide ions respectively, which includes the steps of:
- obtaining said ternary alkaline earth-rare earth sulfides by reacting carbonates of the alkaline earth elements with oxides of lanthanide elements in an atmosphere of flowing hydrogen sulfide;
- hot pressing said ternary alkaline earth-rare earth sulfides for densification thereof;
- and
- hot-isostatic pressing the densified ternary alkaline earth-rare earth sulfides resulting from said step of hot-pressing for further densification thereof.
Dependencies are inferred from the claim text.