The problem of oxide admixtures in zinc sulfide as a material for infrared optics (a review)

Abstract

The paper reports on the main physicochemical properties of zinc sulfide (ZnS) and the features of its application in optics, optoelectronics, and semiconductor technology, as well as the main synthesis methods (synthesis in a solution, self-propagating high-temperature synthesis, and chemical vapor deposition). The harmful effect of the ZnO admixture on the optical and operational properties of zinc sulfide as a starting material for optical ceramics and in a thin film coating is shown. Possible ways of zinc oxide entering the base material during synthesis, storage in air or subsequent heat treatment are considered. The possibility of detecting and estimating the content of oxide admixture (ZnO) in ZnS by methods of substantial chemical analysis has been established. For the first time, approaches were proposed and implemented aimed at weakening the harmful effect of oxide admixtures by binding them with the help of lanthanide sulfides and sulfofluorides, followed by the formation of lanthanide oxosulfides by exchange reactions. The use of the addition of boron oxide (B2O3) with the formation of complex compounds with significantly lower chemical activity and volatility compared to ZnO is considered more promising. The method developed by the authors implies the complete removal of the ZnO impurity by heat treatment of the material with a sulfurizing agent, Sb2S3, the excess of which is removed by heat treatment in a vacuum. This method seems to be more labor-intensive, but more attractive for consumers of zinc sulfide as a material for interference optics.