Thermal properties of Sr-containing iron-phosphate glasses experimental and theoretical approach

P Stoch and I Krakowiak, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 150, 13953-13965 (2025).

DOI: 10.1007/s10973-025-14316-3

Iron-phosphate glasses, widely used and versatile, depend on their chemical composition for various applications. Among others, they are promising materials in toxic waste vitrification because of their high chemical durability and relatively low processing temperature and time. They are a novel group of glasses that are considered in the vitrification of radioactive waste, especially those that cannot be treated using conventional borosilicate ones. Since strontium isotopes are one of the main fission products present in the waste, the influence of Sr on the thermal and structural properties of the glasses is an important factor. Strontium-containing iron-phosphate glasses were subjected to thermal properties, glass devitrification, and molecular dynamics simulation studies. In the paper, a new method of glass transition temperature determination based on the simulations is proposed. The theoretically derived temperature is compared to the experimental. The simulation studies revealed that strontium creates enriched and depleted regions across the glass network. The glass transition temperature depends on the flexibility of the regions, and below c.a. 30 mol% of SrO decreases and above increase. The effect is correlated with the formation of the Sr-rich continuous phase. The glass thermal properties are also discussed in light of changes in the glass network topology due to the SrO content increase.

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