Can glass stability parameters infer glass forming ability?

Edgar D. Zanotto,Luciana A. Souza,Eduardo B. Ferreira,Marcio L.F. Nascimento

doi:10.1016/j.jnoncrysol.2005.08.013

Edgar D. Zanotto, Luciana A. Souza + Show 2 more

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https://doi.org/10.1016/j.jnoncrysol.2005.08.013

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Abstract

Glass-forming ability (GFA) is the easiness to vitrify a liquid on cooling, while glass stability (GS) is the glass resistance against devitrification on heating; but it is questionable if there is any direct relationship between these two parameters. Therefore, to test this possibility, we assess and compare GFA and several GS parameters through quantitative criteria. GFA and GS were calculated for six stoichiometric glass forming oxides that only present surface (heterogeneous) crystallization in laboratory time scales: GeO2, Na2O·2SiO2, PbO·SiO2, CaO·Al2O3·2SiO2, CaO·MgO·2SiO2 and 2MgO·2Al2O3·5SiO2; plus Li2O·2SiO2 and Li2O·2B2O3 that, in addition to surface nucleation, also present homogeneous (internal) crystallization. We gauge GFA by the critical cooling rate, qcr, which was calculated from an estimated number of heterogeneous nucleation sites per unit surface, Ns, and from experimental crystal growth rates, u(T), assuming a detectable surface crystallized fraction Xc=0.001. We define GS parameters by fourteen different combinations of the following characteristic differential thermal analysis (DTA) or differential scanning calorimetry (DSC) temperatures: the glass transition temperature (Tg), the onset crystallization temperature on heating (Txh), the peak crystallization temperature on heating (Tch), and the melting point (Tm). To obtain the experimental GS parameters for each glass we carried out DSC runs using coarse and fine powders, and completed the necessary data with literature values for Tm. The results for fine and coarse particles were quite similar. Most of the GS parameters that consist of three characteristic DSC temperatures show excellent correlation with GFA, however, rather poor correlations were observed for parameters that use only two characteristic temperatures. We thus demonstrated that certain, but not all GS parameters can be used to infer GFA.

Highlights

There is consensus that any material can vitrify if cooled from the molten state to the glass transition temperature, Tg, at a rate fast enough to prevent crystallization
These data are plotted against the reduced temperature T/the melting point (Tm) to allow a comparison of all glasses
The highest maximum growth rate is that of Li2O Æ 2B2O3 (LB2) (3 · 10À3 m/s) and the slowest refers to GeO2 (9 · 10À8 m/s)

Summary

Introduction

There is consensus that any material can vitrify if cooled from the molten state to the glass transition temperature, Tg, at a rate fast enough to prevent crystallization. The slowest a material can be cooled down to Tg without crystallization the easiest it is vitrified, and this property is denominated glass forming ability (GFA). One can define a critical cooling rate, qcr, to avoid a crystalline fraction higher than Xc on cooling a liquid. It is quite difficult to accurately measure qcr and the complexity increases for reluctant glass formers that require very high cooling rates. If one could devise indirect ways to estimate GFA would avoid exhaustive laboratory investigations, and this is a key step for efficient development of new glasses and glass-ceramics

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