Enhancement of oxidation resistance of CoSb3 thermoelectric material by glass coating

Abstract Materials based on CoSb 3 are ranked among thermoelectrics with the highest conversion rate, however in service they tend to rapidly lose the useful properties as a result of oxidation or sublimation. Glass coatings were designed in this work to protect CoSb 3 against degradation in air at elevated temperatures. The coatings were based on borosilicate glass with a high content of titania. Their chemical composition was tailored to match the coefficient of thermal expansion (CTE) of the substrate (9.2 · 10 − 6  K − 1 ) and to secure thermal stability and low softening point of glass. The coatings deposited by a simple dipping technique were fired in the temperature range 700–740 °C. Evaluation of these coatings was based on accelerated oxidation tests at 600 °C for 20 h. The micro- and nanostructure of the CoSb 3 /glass coating interface were examined by means of advanced electron microscopy. The coating appeared to have good adherence and to effectively protect the thermoelectric substrate against antimony loss and oxidation up to 600 °C.