Glass-ceramic systems, oxyfluoride

The following section of this chapter will present the most commonly studied oxyfluoride glass-ceramic systems. The synthesis method is reported for each system. However, as... 

In case of the fabrication ofoxide/fluoride composite materials, trifluoroacetate sols are mixed with solutions of other compositions. For example, an aUcoxide solution composed of tetramethylorthosilicate (TMOS), methanol, water, and A,iV-dimethylformainide (DMF) is mixed with trifluoroacetate sols in preparing Si02 -based oxyfluoride glass-ceramics (Fujihara, 1999). However, optimal experimental conditions for the silica system alone are not necessarily suitable for the preparation of composites. Factors are concerned such as compositions, pH values, and types of catalysts. Because TFA acts as an acid catalyst in the processing ofSiOa-based systems, overall solution compositions should be simplified by understanding a role of each constituent (Fujihara, 2000c). 

In this chapter, we describe different transparent oxyfluoride systems doped with lanthanide ions. We examine the conditions that can lead to a perfectly controlled crystallization process and also the conditions that insure an efficient segregation of the rare-earth ions inside crystallites. Finally, we discuss the optical properties of glass-ceramics, in terms of absorption, emission and lifetimes. We establish a comparison between their optical properties and those of glasses and single-crystals. 

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