Corrosion behavior of thermoelectric clathrates α- and β-Eu8Ga16−Ge30+ in air

Abstract The corrosion of thermoelectric clathrates α- and β-Eu 8 Ga 16− x Ge 30+ x is studied under static air (DSC/TG) up to 650 °C. Oxidation product layers with thicknesses of 10.5 μm (α-Eu 8 Ga 16− x Ge 30+ x ) and 4.5 μm (β-Eu 8 Ga 16− x Ge 30+ x ) are formed. The oxidation begins at 360 and 380 °C, respectively. XRD pattern of the β-Eu 8 Ga 16− x Ge 30+ x oxidized layer shows Ge and four Eu 2 O 3 reflections; while α-Eu 8 Ga 16− x Ge 30+ x data (sample crushed and grinded) shows α-Eu 8 Ga 16− x Ge 30+ x reflections (majority phase), two EuGa 2± x Ge 4∓x strongest reflections and Ge (minority phases). These results indicate the amount of oxides is very small or they are amorphous. High temperature powder XRD measurements on α-Eu 8 Ga 16− x Ge 30+ x under air confirm the oxidation onset temperature determined in DSC studies.