Preparation and Characteristics of IR Window Grade Zinc Sulphide Powder

Zinc sulphide (ZnS) is an important II-VI compound well-Known for the electrooptic applications. It is also one of the most suitable materials for the fabrication of IR transmitting domes and windows because of its transmission in the IR region of (2-12 micron) the spectrum as well as its excellent thermo - mechanical properties. The ZnS domes and windows are prepared by hot pressing or hot isostatic pressing (HIP) of optical quality grade ZnS powder. This paper describes the preparation of optical quality grade ZnS powder using a modified acid process maintaining a constant pH. The resulting ZnS powder is subjected to thermal treatment in different atmospheres and at different temperatures. The ZnS powder thus obtained has been characterised by chemical analysis partical size measurement IR spectrophotometry XR-D and XR-F analysis. The role of various experimental parameters involved, e.g., concentration of ZnSO/sub 4/ solution firing temperature and firing atmospheres is investigated. A transmission of 69 per cent was achieved after HIP of the ZnS powder prepared by this method.