A Perspective on the Particle-Based Crystal Growth of Ferric Oxides, Oxyhydroxides, and Hydrous Oxides

Abstract

The iron oxides, oxyhydroxides, and hydroxides, which are commonly referred to as simply the iron oxides, are important materials at and near the Earth’s surface and in a wide range of industrial settings. The reactivity, phase transformations, and aggregation state of iron oxide minerals are fundamentally linked. The size, microstructure, and morphology of iron oxide crystals are path dependent, and specific features can potentially be linked directly to the crystal growth mechanism(s) that produced them. Many conclusions regarding crystal growth mechanism rely on characterization of the final crystals, and this approach has been fruitful. The iron oxides literature contains many reports of crystals with textures, morphologies, and microstructures that are consistent with particle-based crystal growth. However, multiple crystal growth mechanisms can operate simultaneously, which lead to erasure of features produced at earlier stages of crystal growth. Thus, time-resolved and in situ materials characterization is crucial to elucidating the crystal growth mechanisms of iron oxides.