Nucleation and Crystallization of Na ₂ O · 2CaO · 3SiO ₂ Glass by Differential Thermal Analysis

Abstract

The nucleation and crystallization of the Na 2 O · 2CaO · 3SiO 2 (NC 2 S 3 ) glass were studied by differential thermal analysis (DTA), and a (nucleation rate—temperature)‐like curve was determined by plotting either the reciprocal of the temperature corresponding to the crystallization peak maximum, 1/ T p , or the height of the crystallization peak, (δ T ) p , as a function of nucleation temperature, T n . The temperature where nucleation can occur for this glass ranges from 550° to 650°C and the temperature for maximum nucleation is 600°± 5°C. Both temperatures are in excellent agreement with those determined by the classical technique of nucleation followed by isothermal crystallization. The activation energy for crystallization, E c , for this glass is the same for surface and/or bulk crystallization, and is 370 ± 15 kJ/mol. The analysis of the crystallization data with the Kissinger equation yelds the correct value for E c only when crystal growth occurs on a fixed number of nuclei. When a majority of the nucleation occurs during the DTA measurements, a modified Kissinger equation must be used to calculate E c . E c is also independent of the heating rate when determined using a single‐crystallization‐peak analysis technique. The single‐peak analysis technique is useful for a rapid determination of E c or when only a small amount of sample is available.