Si-O-C amorphous coatings for high temperature protection of In0.4Co4Sb12 skutterudite for thermoelectric applications.

High temperature corrosion of thermoelectric materials is one of the most important issues linked with their application for power generation, especially in terrestrial conditions. The high chemical affinity of elements composing thermoelectric material to oxygen results in continuous degradation at high temperatures of most state-of-the-art materials. This issue is also well recognized in the case of antimonide skutterudites. The simplest way to protect against this process is the use of coatings. Complicated geometry of thermoelectric module favors coatings that can be deposited in a simple way on an assembled module. Such an opportunity, besides good thermal stability and appropriate thermal and electrical properties, is provided by amorphous silicon oxycarbide Si-O-C coatings. In this work, the results on Si-O-C coatings deposited on In0.4Co4Sb12 skutterudite are presented. The influence of heat treatment temperature and substrate roughness on the deposited layer is shown. Protective properties of the Si-O-C layer are presented by comparison of electrical conductivity and Seebeck coefficient of coated and uncoated samples, before and after isothermal oxidation in air at 430 °C for 24 h. In such conditions, the uncoated samples are distinctly oxidized (weight gain of 2.4%) with strongly affected electrical properties, while the coated samples show a slight weight gain of 0.1% and almost unchanged electrical properties. [ABSTRACT FROM AUTHOR]