The spectral properties and thermal stability of NbTiON solar selective absorbing coating

A new solar selective absorbing coating of NbTiON/SiON was prepared on Cu substrate using a reactive magnetron sputtering method. The new coating exhibits a high absorptance (α) of 0.95 and a low emittance (ε) of 0.07, and the thickness of NbTiON and SiON layers was optimized to achieve high solar selectivity. The spectral properties (α/ε) of the coating on Cu substrate are stable (0.94/0.08) even after heat-treatment at 500 °C in vacuum for 40 h, but decreased at 600 °C. If the substrate is replaced by stainless steel (SS), the coating exhibits better stability, which indicates its potential applications in intermediate temperate solar absorber.