Non-isothermal crystallization kinetics of CaO-SiO2-B2O3-TiO2 glass studied by differential thermal analysis in the case of “site saturation”

Abstract

Crystallization characteristics of the CaO-SiO2-B2O3-TiO2 glass have been studied using scanning electron microscopy, X-ray diffraction and differential thermal analysis techniques. The crystallization kinetic parameters of this glass were estimated under non-isothermal conditions using the Matusuta-Sakka equation. Glass with fine particles (<74 μm), case referred to as ‘‘site saturation’’, was used to obtain the non-isothermal differential thermal analysis curves. Bulk glass-ceramics with dense and nonporous morphology are obtained after the heating treatment indicating the strong heterogeneous nucleation at the junction of gain boundaries in the case of “site saturation”. As the content of TiO2 exceeds 18%, the predominant crystal phase changes from CaSiO3 to CaTiSiO5, until CaTiSiO5 becomes the only crystal phase of the glass at 26% TiO2. The crystallization activation energies, EG, are in the range of 245–514 kJ/mol. As TiO2 increases from 10% to 18%, crystallization ability of the glass decreases gradually and the crystallization corresponds to one-dimensional growth mechanism or surface crystallization, while as TiO2 further increases from 18% to 26%, not only does the glass show an increasing crystallization ability, but also the crystal growth changes to the two-dimensional growth mechanism. Within the range of 22%–26%, TiO2 plays the role of strengthening the crystallization of the glass by acting as a major component in the glass to form Ti-bearing compound. From the standpoint of glass-ceramics preparation, the glass containing more TiO2 (such as 26%) with CaTiSiO5 as the only crystal phase is favorable in the present study.