Effect of the nanostructuration of skutterudite materials on their oxidation behaviours

A thermoelectric generator is a powerful system made of both n-type and p-type semiconductors able to produce electricity by the action of heat. Among the thermoelectric materials, the skutterudites of the CoSb₃ type doped with various other elements are known to have interesting thermoelectric properties. Thermal conductivity can be reduced and the figure of merit can be improved by nanostructuration. Skutterudites are envisaged for a use at high temperature under oxidative atmosphere (e.g. air) and may suffer degradation in service, which may drastically decrease their lifespan. The possible effect of nanostructuration on the oxidation of skutterudites has been investigated in this work. Several nanostructured skutterudites have been oxidized under a flow of synthetic air, at 650 K and at 800 K for several durations (15, 50, 100 and 1000 h). The oxide layers formed on surface were observed and their characteristics (thickness, structure⋯) were compared to those obtained for their microstructured versions. As a result, depending on the chemical composition of the skutterudite material, the nanostructuration can improve or not its oxidation behaviour in air.