Crystallization Kinetics of a Lithia-silica Glass

The crystallization kinetics of a 40Li2O · 60SiO2 (mol%) glass were studied using DTA and both isothermal and nonisothermal DSC techniques as a function of (1) particle size of the glass powder, (2) crucible material, e.g., alumina or platinum, (3) furnace atmosphere, e.g., nitrogen, oxygen, or argon, and (4) surface pretreatment of the glass powder with deionized water, HCl, or HF. the kinetic parameters for crystallization, namely, the activation energy, E, frequency factor, v, and Avrami exponent, n, for a particular sample particle size are in close agreement for all three techniques. E and v both decrease while n increases (from 0.9 to 3.0) as the particle size of the glass powder increases from 40 to ∼250 μm, whereupon these parameters become fairly constant for larger particles. Neither the furnace atmosphere nor crucible material had a significant effect on E, v, or n. Washing the glass with deionized water, HCl, or HF before the measurements decreased the crystallization temperature by 25° to 30°C. E and v remain unchanged by this treatment, but n decreased from 3 to 1.6 for a sample of particle size ∼250 μm