A novel Mo/Al2O3 spectrally selective solar absorber coating is deposited onto stainless steel (SS) substrates using magnetron sputtering method, which exhibits a high absorptance (α) of 0.90 and a low emittance (ε) of 0.08. In order to investigate the thermal stability, the SS/Mo/Al2O3 coatings are annealed in air and vacuum at different temperatures. The surface morphology, microstructure, composition distribution, diffusion and optical properties before and after high-temperature annealing are characterised by scanning electronic microscopy (SEM), atom force microscopy (AFM), X-ray diffraction (XRD), micro-Raman spectroscopy, UV–vis spectrophotometer and emissometer. Experimental results indicate that the coatings are stable in air at 350°C. The values of solar absorptance and emittance below 350°C are 0.87–0.90 and 0.06–0.08, respectively. The coatings remain stable after annealed at 600°C in vacuum for 2 h with a good spectral selectivity (α/ε) of 0.89/0.06.
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