Abstract
The kinetics of devitrification of fluoride glasses stabilized by magnesium fluoride when heated for some time between the glass transition and melting temperatures. The crystallization kinetics of AlF 3 -YF 3 -PbF 2 -CdF 2 -MgF 2 glass prepared by melting the halide powders were studied by differential scanning calorimetry (DSC). The heating rate varied between 2 and 10 Kmim -1 . Arami’s exponent (n) obtained by a non-isothermal method was 1.5 and 2.5 for a AlF 3 -YF 3 -PbF 2 -CdF 2 -xMgF 2 (x= 0, 5, 10) and n > 2.5 for a AlF 3 -YF 3 -PbF 2 -CdF 2 -15MgF 2 . According to the classical interpretation of n, these magnitudes correspond to diffusion controlled growth of crystals. The activation energies for crystallization, (E), varied from 195-326 KJ/mol. These results confirm the improved stability of these glasses, which could be used as base glasses for low phonon energy fluoride glass fibers. Keywords: crystallization kinetics, glass transition, DSC, Avrami’s exponent (n), activation energies (E).
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