Enhanced Strength and Durability in Zinc Sulfide

Variants of ZnS have good transmission properties throughout the visible and infrared regions, however durability and strength have always been issues with this material. Several variants of ZnS are available depending on the transmission requirements in the near infrared region. Recently, improved strength has been demonstrated in aluminum oxynitride (ALON) through post processing and high quality surface finishing. Under the Phase I effort to date, Surmet has evaluated ZnS materials growth and optical fabrication processes, identified potential optical fabrication process improvements, and is in the process of manufacturing equi-biaxial test samples of all three ZnS variants (ZnS, Multispectral ZnS, and Elemental ZnS) to allow an initial evaluation of the impact of these modified processes on strength. Under the Phase II effort, Surmet proposes a two pronged approach. The most promising of the results from the Phase I effort will be further developed and refined. Secondly, additional technologies with the potential to improve ZnS strength will be investigated. These include alternate optical fabrication technologies which may yield polished surfaces with smaller residual flaws, and potentially surface coatings which have been shown to increase flexural strength.