Synthesis of α-cordierite based glass-ceramic from Bayan Obo tailing and fly ash through volume crystallization

The α-cordierite glass-ceramics samples were synthesized from Bayan Obo mine tailing and fly ash through volume crystallization as a result of using (NH₄) H₂PO₄ and MgF₂ as the nucleating and glass network relaxing agents, respectively. The application of some natural impurities within above wastes, i.e., CaO, Na₂O, and K₂O, as the flux to lower the viscosity of the base glass, also contributed to this successful synthesis. The density, bending strength, Vickers hardness, dielectric constant and loss within the 1-10 MHz testing frequency range, and the average coefficient of thermal expansion of the glass-ceramic were characterized at 2.56 g cm⁻³, 113.5 ± 15.87 MPa, 7.04 ± 0.26 GPa, ∼7.3, ∼10⁻² and 1.86 × 10⁻⁶ °C⁻¹ respectively. These properties make this solid waste-derived material a lucrative candidate for replacing the industrial cordierite in metallurgy and construction. The results of this study may serve as a useful example of the re-utilization of solid wastes similar to Bayan Obo tailing with high added value.