Crystallization kinetics in a lithium disilicate glass revisited: Model-free and model-fitting approaches

The present work estimated the crystallization activation energy, E & alpha;, the pre-exponential term, A, and the reaction model, g(& alpha;), of a lithium disilicate glass using model-free and model-fitting approaches. Samples with distinct granulometry (PD1: < 105 & mu;m; and PD5: 600-850 & mu;m) were heated at several rates (0.5 to 30 K/min). Our results show that E & alpha;, A, and g(& alpha;) are susceptible to particle size. PD1 crystallizes in a single step, and the surface mainly governs it all & beta; values. On the other hand, the overall crystallization of PD5 is more complex and can be described by different Avrami reaction models, with n = 1, 1.5, 2, and 3. In addition, we found that the crystallized fraction at the crystallization peak (& alpha;Tp) varies significantly with the particle size and heating rate, which confirms that all the methods that assume that the & alpha;Tp is constant are inadequate to describe the crystallization of glasses over a wide range of heating rates.