Calculation of ternary fluoride glass compositions

Abstract

The recent discovery of a new family of non-oxide glasses based on mixtures of ZrF 4 or HfF 4 with other metallic fluorides by M. Poulain and coworkers offers great potential in optical fiber, window and source/detector application. Due to the limited phase diagram data available for the binary, ternary and multicomponent fluoride systems currently employed to synthesize these glasses most of the progress in identifying new compositions has proceeded along empirical lines. In order to remedy this situation, the CALPHAD method for coupling phase diagram and thermochemical data has been applied to develop a data base covering metallic fluorides. The objective is to permit computation of multicomponent phase diagrams which can be used to identify the composition range where the liquid is most stable. The latter offers opportunities for glass formation as demonstrated by predictions of new metallic glasses. Currently the data base covers combinations of 0.2 ZrF 4(ZF), 0.25 LaF 3(LF) 0.333 BaF 2(BF), 0.333 PbF 2(PF), 0.5 NaF(NF), 0.5RbF(RF), O.5CsF(CF) and 0.5 KF(KF) which have been developed along the lines described earlier for III–V, II–VI and SIALON systems. These results were used to generate computed liquidus contours in LF-ZF-BF and BF-ZF-NF to disclose the range of composition in which the liquid has the greatest stability. These compositions agree well with those in which Poulain and coworkers have discovered glass formation.