Impact of chemical diffusion on crystal growth in sodium borosilicate glasses

• Published in: Journal of non-crystalline solids 2019-01, Vol.503-504, p.313-322
• Main Authors: Pablo, H., Schuller, S., Toplis, M.J., Mostefaoui, S., Mesbah, A., Roskosz, M.
• Format: Article
• Language: English
• Subjects: Chemical diffusion; Chemical Sciences; Cristobalite; Crystal growth rate; Inorganic chemistry; Material chemistry; Sodium borosilicate glasses
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2018.10.013

The link between multicomponent diffusion and crystal growth has been investigated in a sodium borosilicate glass of interest to the nuclear industry. The growth rate of cristobalite, the principal crystal formed in this system, was studied between 700 °C and 900 °C. The growth rate was found to be linear with time and had an activation energy of 60 ± 12 kJ.mol−1 which is close to the activation energy of sodium self-diffusion. Analysis of compositions around crystals and in the bulk of the glass revealed compositional gradients assigned to multicomponent diffusion. A diffusive mechanism involving exchange between silicon and boron appears to drive melt compositions near the crystals while in the bulk of the glass, another diffusive mechanism is predominant, consisting of exchange of silicon and sodium, justifying the value calculated for the activation energy of crystal growth. These results were then used for modeling growth rates in our glass. •A borosilicate glass with molar composition 68SiO2-18B2O3-14Na2O mainly crystallizes cristobalite between 700 °C and 900 °C.•The linear cristobalite growth has an activation energy close to the activation energy for sodium self-diffusion.•The evolution of compositions around crystals during crystal growth is driven by chemical diffusion.•The growth rate can be modeled using the dominant eigenvalue of the diffusion matrix as a diffusion coefficient.