Unmixing inducing polymerization of a sodium-molybdenum borosilicate network

• Published in: Materials letters 2025-02, Vol.381, p.137776, Article 137776
• Main Authors: Pereira, Luiz, Schuller, Sophie, Donatini, Adrien, Wadsworth, Fabian B., Neuville, Daniel R., Dingwell, Donald B., Ligny, Dominique De
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Glass; In-situ high-temperature measurement; Liquid-liquid phase separation; Nuclear waste glasses; Raman spectroscopy
• ISSN: 0167-577X
• DOI: 10.1016/j.matlet.2024.137776

•Mo-bearing borosilicate melt can undergo unmixing.•Alkali- and Mo-rich droplets form at high temperature.•In-situ Raman spectroscopy can be used to measure melt polymerization in response to unmixing.•This droplet formation polymerizes the silicate component on the network.•This droplet formation polymerizes the borate component on the network. Glass network polymerization critically influences rheological behavior and with it the kinetics and dynamics of nuclear waste immobilization. Molybdenum-bearing borosilicate melts may undergo unmixing and rheological changes, which is dominantly controlled by the associated chemical modifications of the melt network. Here, we obtain in-situ (500–940 °C) Raman spectra to probe structural changes of a sodium-molybdenum borosilicate melt undergoing unmixing. The extraction of alkali and molybdenum to form droplets induces polymerization of the residual borosilicate network. Conversely, the opposite phenomenon is observed during droplet re-dissolution. This work provides new insights into the polymerization of a molybdenum-bearing borosilicate composed of two composition sets due to a miscibility gap and has direct contributions for the immobilization of nuclear wastes.