Microstructure and electrical characterization of SixC1 − x/Al2O3 composite coatings for nuclear fusion applications

• We prepared SixC1 − x/Al2O3 coatings with three Si contents by magnetron sputtering.
• We studied the influence of Si content on microstructure and electrical property.
• Polycrystalline silicon and nanocrystalline carbon are detected in different coatings.
• The resistivity of the coatings has been studied from room temperature to 500 °C.
• Amorphous and nanocrystalline carbon could increase the coating resistivity to 108 Ω cm at 500 °C.

SixC1 − x/Al2O3 composite coatings have great potential to be the coatings of fusion reactor material because of their high electrical resistivity and tritium resistivity properties. SixC1 − x/Al2O3 coatings with three different Si concentrations were prepared by magnetron sputtering. Coating compositions, and microstructures of SixC1 − x/Al2O3 coatings are investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that SixC1 − x in SixC1 − x/Al2O3 coatings is mainly amorphous while a small amount of polycrystalline silicon exists in Si0.62C0.38 layer and nanocrystalline carbon is observed embedded in Si0.40C0.60 layer. The electrical properties of the composite coatings from room temperature to high temperature are studied. The resistivities of three coatings of different Si concentrations at room temperature and at 500 °C are 6.17 × 107 Ω cm, 2.62 × 1010 Ω cm, 7.10 × 1011 Ω cm and 6.37 × 106 Ω cm, 8.64 × 107 Ω cm, and 7.54 × 108 Ω cm, respectively. The carbon-rich samples exhibit a better electrical insulation characteristic.