Preparation and structural evolution of Mo/SiOx protective coating on CoSb3-based filled skutterudite thermoelectric material

• A Mo/SiOx multilayer film was deposited on a Ce0.9Fe3CoSb12 skutterudite surface.
• The interdiffusion of Mo and Sb resulted in the formation of a Mo3Sb7 layer.
• The Mo3Sb7 layer facilitates adhesion to skutterudite, and blocks further interdiffusion.
• Sb sublimation in Ce0.9Fe3CoSb12 was greatly suppressed by the Mo3Sb7/Mo/SiOx coating.

A Mo/SiOx multilayer film was deposited on a Ce0.9Fe3CoSb12 skutterudite surface as a protective coating by magnetron sputtering. A thermal aging test was conducted under vacuum at 823–923 K, and the microstructural evolution of the multilayer film and the effects of the protective coating on the suppression of Sb sublimation were investigated. The as-prepared Mo layer is crystallized in a body-centered cubic structure with preferred orientation of the (1 1 0) plane parallel to the substrate, whereas the SiOx layer is amorphous. The formation of a Mo3Sb7 interlayer between the skutterudite and coating was observed after the high temperature thermal aging that enhanced the adhesion between the coating and the skutterudite. The Mo3Sb7 layer is chemically stable at high temperatures; therefore, it blocks the further diffusion of Mo and Sb on the boundary. The Mo3Sb7/Mo/SiOx multilayer coating can effectively suppress Sb sublimation, enabling high temperature applications of the CoSb3-based thermoelectric device.