Thermal Characterization and Theoretical Optical Assessment of Fe-Rich Scoria-Based Glasses Prepared from Natural and Industrial Waste Resources

In this study, five Fe-rich scoria-based glass compositions were prepared using natural scoria, recycled glass cullet, limestone, and magnesite through the melt-quenching technique at a temperature of 1400 °C for 2 h. The effect of Fe₂O₃ content (2.9–14.5 wt%) on the thermal behavior, crystallization, density, and predicted optical properties of glass was investigated. Differential thermal analysis revealed that increasing Fe₂O₃ content leads to a variation in glass transition (Tg = 632–669 °C) and an increase in softening temperatures (Ts = 711–737 °C), accompanied by an expanded thermal stability window (∆T = Tx − Tg) up to 254 °C, indicating enhanced resistance to crystallization and improved thermal stability. The density measurement showed a non-monotonic variation with composition, due to the combined effect of Fe₂O₃ enrichment and network structural modification. The crystallization behavior of the Fe-rich scoria-based glass (H50) was further studied after heat treatment at 900 °C and at 950 °C using XRD and SEM analysis. The heated samples exhibited the formation of crystalline phases including diopside, gehlenite, wollastonite, maghemite, and anorthite. While SEM observation revealed progressive crystal growth and microstructural densification with increasing heat treatment temperature, indicating the transformation from glass to glass–ceramic. In addition, a semi-empirical optical assessment based on literature-derived models suggested increased absorptance from 97.26% to 98.83% and reduced reflectance with increasing Fe₂O₃ content. However, these optical parameters show theoretical estimates and require experimental validation. These findings demonstrate the potential of Fe-rich scoria-based glasses as thermally stable materials for high-temperature and energy-related applications while using natural and industrial waste sources.