Enhancing crystallization and structural modification in SiO₂-CaO-Al₂O₃ glass-ceramics using mineral-based Mn source

This work studies the effects of adding natural manganese ore in amounts between 0 and 15 wt% on the crystallization and microstructure of SiO₂-CaO-Al₂O₃ (SCA) glass-ceramics. The samples were prepared by melting and quenching with feldspar and calcium carbonate as base materials, followed by synthesizing at different temperatures. Characterization and physicochemical tests confirmed that the addition of manganese ore improves the crystalline phase formation of anorthite, rhodonite, and bustamite. Increasing the manganese content in the samples showed higher levels of non-bridging oxygen to total oxygen (NBO/T) ratio, which suggests more network depolymerization of the glass structure, which is known to enhance crystallization. X-ray diffraction and scanning electron microscopy clearly showed that rhodonite and bustamite grains grew larger and sharper at 1000 °C and that new Mn-containing phases formed, proving better long-range order. Physicochemical tests revealed manganese ore-rich samples were of higher hardness, lower water absorption, and higher corrosion resistance than their manganese ore-free counterpart. However, adding too much manganese ore (over 10 wt%) led to excessive grain growth and internal flaws, underscoring the need for careful compositional balance.