Hard antireflective films of SiAlON for zinc sulfide in 3–5 μm regions

SiAlON films with antireflective and protective functionality for zinc sulfide were prepared by an ion beam sputtering method. A great transmittance improvement (at 3.8 μm) of 25.1% has been realized for zinc sulfide substrate. At the same time, the in situ high temperature transmittance was also recorded and it was proven that the SiAlON films on zinc sulfide window materials can keep thermal stability well at temperature as high as 250 °C in the region of 3–5 μm. The micro hardness of the zinc sulfide was improved by 75% in average after being coated with SiAlON films, and the SiAlON films possess good behaviors in harsh environmental tests including adhesion, abrasion, moisture, and thermal shock circle.