Evaluation of the Effect of Fe2O3 as a Sintering Additive on Densification, Microstructure, and Thermal Stability of Al2O3

This study investigates the fabrication of alumina-based (Al2O3) ceramics using pressureless sintering, employing hematite (Fe2O3) as a sintering aid. Fe2O3 powders were synthesized via combustion and incorporated into Al2O3 concentrations of 0.5, 1.0, and 2.0 wt.%. The samples were sintered at 1400 °C and characterized by X-ray diffraction (XRD) with Rietveld refinement, thermogravimetric analysis (TG/DTG), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and density measurements using the Archimedes method. The results demonstrated that the addition of Fe2O3 increased the densification of Al2O3 ceramics, with the highest densification (~85%) observed in samples containing 1.0 and 2.0 wt.% Fe2O3. XRD analysis identified only the corundum phase of Al2O3, suggesting that Fe2O3 was incorporated without forming secondary phases. However, Rietveld refinement calculations revealed distortions in the unit cell volume, which contributed to lowering the melting temperature of Al2O3, thereby facilitating sintering. SEM images showed that Fe2O3 acted as a grain growth inhibitor, resulting in finer microstructures with smaller grains. EDX mapping indicated that Fe ions preferentially accumulated in regions with higher pore concentrations. Thermal analysis demonstrated improved thermal stability in Fe2O3-containing samples. Overall, the study confirms that Fe2O3 serves as an effective sintering aid, enhancing densification and thermal stability while refining the microstructure of Al2O3 ceramics. These findings contribute to the development of optimized ceramic materials for high-performance applications.