Al2O3-Fe2O3 composites obtained by colloidal processing route and sintered by spark plasma sintering: Microstructure and properties

Al₂O₃-Fe₂O₃ ceramic composites were prepared for the first time by colloidal synthesis from alumina powder and Fe(NO₃)₃·9(H₂O) using water as the dispersion medium. Doped alumina was treated at 600 °C under air atmosphere to thermally decompose the ferric nitrate and obtain Al₂O₃ with Fe₂O₃ nanoparticles on the surface. Five Fe₂O₃ contents were studied (1, 2.5, 5.0, 10.0, and 20.0 wt%). Monolithic alumina was used as a reference to analyze the influence of the Fe₂O₃ content on the properties of the composite. Sintering was carried out in a spark plasma sintering (SPS) apparatus under a vacuum atmosphere at 1400 °C for 3 min, with an applied pressure of 80 MPa.

The mechanical and electromagnetic properties of the composites were correlated with the microstructure of the composites. This way, the presence of the Fe₂O₃ nanoparticles promoted a fine-grained structure, which leads to an increase in the fracture toughness in the case of the composites with <5 wt% Fe₂O₃. The addition of Fe₂O₃ is deleterious to the mechanical resistance in the three-point bending test. Regarding electromagnetic properties, all the samples present a soft magnetic behavior with coercive fields. The samples with the largest Fe₂O₃ content (10 and 20 wt%) show a noticeable transverse Kerr effect, ranging up to 0.15% in the UV region.