Sol-gel processing of fluoride and oxyfluoride materials

Producing fluoride and oxyfluoride materials is not easy because of the potential toxicity of fluorinated compounds and gases. Sol-gel processing has been used to produce fluoride and oxyfluoride materials in two ways. In the first case, the composition is formed from oxide precursors, followed by a reactive treatment in HF to fluorinate the composition. In the second case, trifluoroacetate precursors or metal alkoxides in trifluoroacetic acid are used to form the gel or thin films directly. The principal motivation for using sol-gel routes to prepare glassy fluorides and oxyfluorides is that they have useful optical applications.