High-energy plasma dynamic synthesis of multiphase iron oxides containing Fe₃O₄ and ε-Fe₂O₃ with possibility of controlling their phase composition

Iron oxides, especially well-known magnetite (Fe₃O₄) and relatively new ε-Fe₂O₃ phase, attract a scientific and practical interest due to their unique magnetic properties. Despite the large number of known methods for synthesizing Fe₃O₄, obtaining the ε-Fe₂O₃ phase is still remaining an urgent scientific task. This paper presents the studies on the possibility of controlled synthesizing the pointed out iron oxide phases in a single short-term high-energy plasma dynamic process. It is established that the process energy directly affects the phase composition of obtained iron oxides. At higher energies, the products are characterized with the dominance of the ε-Fe₂O₃ phase (up to ∼65 wt %) presented in the form of nanosized crystallites, while at low energies micron-sized hollow spherical particles attributed to Fe₃O₄ are synthesized (up to ∼75 wt %). By optimizing the synthesis process it is possible to reach the ε-Fe₂O₃ phase yield up to ∼90 wt %. The change in the phase composition depending on the initial energy parameters directly affects the magnetic characteristics and magnetic behavior of the synthesized iron oxide products.