Effect of Fe₂O₃ on the Structure, Physical Properties and Crystallization of CaO-Al₂O₃-SiO₂ Glass

The calcium aluminosilicate-based glasses (CaO-Al₂O₃-SiO₂, CAS) with different Fe₂O₃ content (0.10wt%, 0.50wt%, 0.90wt%, and 1.30wt%) were prepared by traditional melt-quenching method. The glass network structure, thermal and mechanical properties, and crystallization behavior changes were investigated by nuclear magnetic resonance spectrometer, Fourier-transform infrared spectro-photometer, X-ray diffractometer, differential scanning calorimetry and field emission scanning electron microscope measurements. The change of Qⁿ in glass structures reveals the glass network connectivity decreases due to the increasing content of Fe₂O₃ addition, resulting in the increasing of non-bridging number in glass structure. The glass densities slightly rise from 2.644 to 2.681 g/cm³, while Vickers’s hardness increases at first, from 6.469 to 6.901 GPa, then slightly drops to 6.745 GPa, with Fe₂O₃ content increase. There is almost no thermal expansion coefficient change from different Fe₂O₃ content. The glass transmittance in visible range gradually decreases with higher Fe₂O₃ content, resulting from the strong absorption of Fe²⁺ and Fe³⁺ ions. The calculated activation energy from thermal analysis results first decreases from 282.70 to 231.18 kJ/mol, and then increases to 244.02 kJ/mol, with the Fe₂O₃ content increasing from 0.10wt% to 1.30wt%. Meanwhile, the maximum Avrami constant of 2.33 means the CAS glasses exhibit two-dimensional crystallization. All of the CAS glass-ceramics samples contain main crystal phase of anorthite, the microstructure appears lamellar and columnar crystals.