Optical property and thermal stability of Mo/Mo–SiO₂/SiO₂ solar‐selective coating prepared by magnetron sputtering

Abstract

Abstract Mo/Mo–SiO 2 /SiO 2 solar‐selective coating for high‐temperature solar thermal application is prepared on quartz glass by direct‐current (DC) and radio‐frequency (RF) co‐sputtering. The normal solar absorptance α n = 0.95 and thermal emittance ε n = 0.097 (353 K) are obtained through process optimization. The normal reflectance R n ( λ ) before and after 1073 K vacuum annealing, are measured by ultraviolet–visible–infrared (UV–VIS–IR) and Fourier transform infrared (FT‐IR) spectroscopy. There is only a slight increase in R n ( λ ) in IR region after annealing, which results in a lower ε n = 0.075 (353 K). The crystallized grain of Mo in the coating, obtained from XRD pattern, increased from 23 to 60 nm after vacuum annealing. These phenomena are mainly caused by the change of crystal state and reflectance of Mo IR layer according to the comparison of R n ( λ ) and XRD patterns of Mo/SiO 2 and Mo–SiO 2 /SiO 2 tandem films. magnified image The near‐normal reflectance of Mo/Mo–SiO 2 /SiO 2 solar‐selective coating before and after 1073 K vacuum annealing.