High-temperature oxidation of CoGa: Influence of the crystallographic orientation on the oxidation rate

The crystallographic orientation plays an important role in high-temperature oxidation of the intermetallic compound CoGa. When CoGa is exposed to air at elevated temperatures, the oxide β–Ga₂O₃is formed, and different scale growth rates are observed, depending on the crystallographic orientation of the CoGa grains. This dependence is a consequence of the anisotropy of the gallium diffusion rate through the β–Ga₂O₃scale and of a topotaxial orientation relationship occurring between β–Ga₂O₃and CoGa. The combination ofex situtechniques, such as transmission electron microscopy and electron backscatter diffraction with optical microscopy, appliedin situresulted in a thorough understanding of these relations and of the oxidation process in general.