EROSION RESISTANT FLIR WINDOWS: COLORLESS ZnS

摘要

A water-clear Zinc sulfide (ZnS) has been developed and characterized. This material possesses good optical transmission over the wavelength range of 0.34 to 12 microns and is useful in many multispectral applications. This water-clear ZnS is produced by initially making ZnS by chemical vapor deposition (CVD) and then processing the material by hot isostatic pressing (HIP). The optimum CVD and HIP parameters for producing water-clear ZnS were established in this program. Because of the high temperatures required in the production processes, water-clear ZnS exhibits larger crystallites and decreased rain-erosion resistance than standard CVD ZnS. A number of surface and bulk treatments were investigated in an attempt to increase the hardness and improve its rain-erosion resistance. Two approaches appear promising. The first involves the incorporation, either by thermal diffusion or during the CVD process, of cadmium (Cd) atoms into the ZnS lattice to produce strain. The second approach would involve the deposition of a thin layer of CVD ZnS onto the water clear material analogous to the previously developed ZnS/ZnSe sandwich material. Other treatment processes investigated involved grain refinement, thermal tempering, ion implantation, pulsed electron beam annealing (PEBA), and surface coatings. None of these treatments appeared to either provide increase hardness or to be practical techniques for optical materials. A large number of optical, physical and mechanical parameters of water-clear Zn/S were measured. These data should allow optical engineers and designers to use this material in various electro-optical systems.