The most recently identified iron oxide polymorph


The most recently identified iron(III) oxide polymorph, ε-Fe2O3, shows the highest coercivity among all known metal oxides (20–22.5 kOe) and could be used as a magnetic recording material for high-density recording media. In addition, its magnetoelectric properties predestine that it could be useful in producing multiple-state-memory elements. Finally, it exhibits ferromagnetic resonance in a millimeter wave region, giving it potential applications in devices for suppressing electromagnetic interference and stabilizing electromagnetic transmittance. Due to the diverse potential applications of all four known iron(III) oxide polymorphs, thermally induced phase transformations of the less thermodynamically stable polymorphs (β-, γ- and ε-Fe2O3) have been studied extensively. The results of these transformations depend on the intrinsic properties of the starting phase (polymorph structure, particle size, particle morphology, surface coating, particle aggregation, incorporation of particles within a matrix) and the nature of the applied treatment. In general, such transformations yield α-Fe2O3 as the final product and are frequently accompanied by particle growth. The two rare iron(III) oxide polymorphs, β- and ε-Fe2O3, undergo direct thermal transitions to α-Fe2O3. However, hollow β-Fe2O3 nanoparticles can be transformed into γ-Fe2O3, demonstrating that the morphology of the starting material can significantly affect the transformation process and permit the evolution of unexpected intermediate iron(III) polymorphs. In the case of γ-Fe2O3, both direct transformations into α-Fe2O3 and two-step transformations via ε-Fe2O3 have been observed, depending on the initial particle size and degree of interparticle interactions (i.e., aggregation, the extent to which the particles are spatially confined). Although thermally induced transformations of Fe2O3 polymorphs have been described at length in the literature, pressure-induced transitions have only been investigated for the most common polymorphs, α-Fe2O3 and γ-Fe2O3. If you are looking for high quality, high purity, and cost-effective Iron Oxide, or if you require the latest price, please email contact mis-asia.

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