Structure, thermal stability and chromaticity investigation of TiB2 based high temperature solar selective absorbing coatings

Abstract Transition metal titanium diboride (TiB 2 ) is a promising material for the solar selective absorbing coatings due to its favorable spectral selectivity and thermal stability. In this research, spectrally selective TiB 2 /Al 2 O 3 tandem absorber is deposited on stainless steel (SS), which exhibits a high solar absorptance (α s  = 0.93) and a low thermal emissivity (e = 0.11). In this tandem absorber, the TiB 2 acts as the main absorber layer and the Al 2 O 3 acts as an antireflection layer. The tandem absorber coating is systematically characterized by ultra-high resolution scanning electron microscope (SEM), UV–vis-NIR spectrophotometer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Micro-Raman techniques. The thermal stability in vacuum of the SS/TiB 2 /Al 2 O 3 tandem absorber coatings is investigated in the temperature range of 400–800 °C for 2 h and 100 h, respectively. SEM and Raman spectra indicate that the change of surface morphology and chemical composition for the coating result in the degradation of optical performance. With the different annealed temperature, the SS/TiB 2 /Al 2 O 3 tandem absorber coatings exhibit different color, which is further investigated using chromaticity diagram.