Abstract
The aim of this work is the development of a synthesis method for zinc fluoride and the optimization of its preparation conditions, taking into account its high practical significance. In particular, the prospects of its use as a material in interference optics are demonstrated. The advantages of synthesizing ZnF₂ using finely dispersed zinc (zinc powder) and concentrated hydrofluoric acid are shown. It was established that during synthesis, a crystalline hydrate of the composition ZnF₂·4H₂O is formed as an impurity, which negatively affects the properties of the main synthesis product. It was revealed that the hydrate impurity primarily influences the operational characteristics of ZnF₂, since ZnO, a harmful impurity, is formed during thermal treatment. To minimize the negative impact of ZnO impurities, the addition of ZnS was proposed, which binds zinc oxide into oxysulfide-type compounds. Experimental tests confirmed the feasibility of introducing such an additive. It was shown that pure ZnF₂ forms coatings of insufficient strength due to its hygroscopicity. Two samples of ZnF₂–ZnS system materials were synthesized, both of which demonstrated significantly lower hygroscopicity. It was shown that this substantially affects the operational properties of materials with ZnS additives. While the material with the additive containing oxide impurity exhibited unsatisfactory operational properties (the coating degraded), the second, without oxide impurity, demonstrated sufficiently high mechanical strength of the coating, indicating that the goal was at least partially achieved. It was concluded that in this case, the influence of the acid–base factor on the mechanical and optical properties of both the materials themselves and the coatings based on them cannot be excluded. From the interference curves of transmittance and reflectance versus wavelength, the refractive indices of the materials in thin-film coatings were calculated. They are 1.60, 1.72, and 1.61, respectively, for ZnF₂, ZnF₂–ZnS (with and without oxide impurity). A conclusion was made about the possibility of using ZnS without oxide impurity to improve the operational properties of the base material, ZnF₂. In the future, ZnF₂ may be applied not only in interference optics but also as an effective component in glasses transparent in the UV spectral range.