EVALUATION OF CRYSTAL NUCLEATION AND GROWTH FROM CRYSTALLIZATION KINETICS DATA OF NEW HALIDE GLASSES

The thermal properties and the crystallization behaviour of a cadmium halide based glass [(CdF2)(50)(BaCl2)(10)(NaCl)(40)] were analyzed. Th e kinetic nature of the glass transition was used to determine the tem perature dependence of the viscosity and an estimation of the appropri ate drawing temperature for an optical fibre was established. The crys tallization kinetics was studied by using both isothermal and continuo us heating regimes. For cadmium halides, the temperature range for nuc leation was evaluated and for samples previously nucleated the activat ion energy of the growth process was found to be 2.01 +/- 0.08 eV. The empirical nucleation and crystal growth rates were estimated and the temperature-heating rate-transformation diagrams were constructed. The results obtained agree with data and are discussed in the light of mi nimizing the volume of crystals formed during fibre drawing.