Facile synthesis of epsilon iron oxides via spray drying for millimeter-wave absorption

A simple, scalable spray drying method was developed for high-yield epsilon iron oxide (ε-Fe₂O₃) synthesis. The ε-Fe₂O₃ particle size can be tailored by varying the annealing temperature and molar ratio of Fe/Si, producing a high-purity ε-phase. This strategy also enables ferromagnetic resonance tuning, making it potentially usable in millimeter-wave absorbers.