Carbon effects on crystallization kinetics of Li2O-Al2O3-SiO2 glasses

Li2O-Al2O3SiO2 glasses with varied amounts of carbon were prepared by conventional melting. Based on the crystallization kinetics, the crystallization activation energy E, frequency factor v, and Avrami exponent n were determined by differential thermal analysis. A single crystal phase, beta-eucryptite, precipitates in all glasses and no carbonide was detected by X-ray diffraction. Wave length dispersive spectroscopy revealed the incorporated carbon remains in the residual glass phase. Both crystallization activation energy and the logarithm function of frequency factor linearly decrease with the increase of the carbon concentration, while the Avrami exponent remains nearly constant. This is interpreted to indicate that the incorporated carbon has a twofold effect on the crystallization of Lithium aluminium silicate (LAS) glasses: (1) lowers the initial crystallization temperature (2) impedes the diffusion in the glasses, but the former effect is predominant. The addition of 4% by weight of carbon has no detectable effect on crystallization of lithium alumino silicate glasses. (C) 1998 Elsevier Science B.V. All rights reserved.