POLYCRYSTALLINE CHALCOGENIDE CERAMIC MATERIAL

The invention relates to a polycrystalline IR transparent material produced by sintering chalcogenide powder, e.g., ZnS powder, using hot uniaxial pressing followed by hot isostatic pressing. The microstructure of the material described in this disclosure is much finer than that found in material produced using the state of the art process. By using a powder with a particle size fine enough to improve sintering behavior but coarse enough to prevent a lowering of the wurtzite-sphalerite transition temperature, a highly transparent material with improved strength is created without degrading the optical properties. A high degree of transparency is achieved during hot pressing by applying pressure after the part has reached a desired temperature. This allows some degree of plastic deformation and prevents rapid grain growth which can entrap porosity. The crystallographic twins created during this process further inhibit grain growth during hot isostatic pressing.