Kinetics of Crystallization of ZrF ₄ ‐Ba ₂ ‐LaF ₃ Glass by Differential Scanning Calorimetry

The kinetics of devitrification in ZrF 4 ‐BaF 2 ‐LaF 3 (62–33–5 mol % ) glass were studied by isothermal and nonisothermal methods using differential scanning calorimetry. The crystallization reaction followed the Avrami equation, x =1‐exp[—( kt) ], where x is the fraction crystallized after time t . The rate con stant k obeyed an Arrhenius equation, k(s −1 )=6.69 × 10 21 exp image The value of the Avrami exponent, n , bas 3.2×0.2, indicating three‐dimensional crystal growth at a constant number of nucleation sites. Values of kinetics parame ters obtained from isothermal and nonisothermal techniques were in excellent agreement. The heat of crystallization measured from isothermal peaks was computed to be 38.5×3.5 J/g.