Crystallization of heavy metal fluoride glassesThe kinetics of crystallization of a number of fluorozirconate glasses were studied using isothermal and dynamic differential scanning calorimetry and X-ray diffraction. The addition of the fluorides LiF, NaF, AlF3, LaF3 to a base glass composition of ZrF4-BaF2 reduced the tendency to crystallize, probably by modifying the viscosity-temperature relation. ZrF4-BaF2-LaF3-AlF3-NaF glass was the most stable against devitrification and perhaps is the best composition for optical fibers with low scattering loss. Some glasses first crystallize out into metastable beta-BaZr2F10 and beta-BaZrF6 phases, which transform into the most stable alpha-phases when heated to higher temperatures. The size of the crystallites was estimated to be about 600 A from X-ray diffraction.
Bansal, Narottam P. (Rensselaer Polytechnic Inst. Troy, NY, United States)
Bruce, Allan J. (Rensselaer Polytechnic Inst. Troy, NY, United States)
Doremus, R. H. (Rensselaer Polytechnic Inst. Troy, NY, United States)
Moynihan, C. T. (Rensselaer Polytechnic Institute, Troy, NY, United States)