Devitrification of fluoroindate glasses

Most fluoride glasses are likely to devitrify when heated for some time between the glass transition and melting temperatures. The crystallization kinetics of some fluoroindate glasses were studied by isothermal and non-isothermal methods using differential scanning calorimetry. The heating rate a varied between 1 and 10 K min(-1). The value of Avrami's exponent n lay between 1 and 2.5, corresponding to a diffusion-controlled growth of crystals. The apparent activation energy for crystallization, E, varied from 45 to 50 kcal mol(-1). These values of n and E are low by comparison with those of other fluoride glasses, which suggests high stability against devitrification.