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

Abstract

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.