Optical properties and failure analysis of ZrC-ZrOx ceramic based spectrally selective solar absorbers deposited at a high substrate temperature

A tandem layer structured ZrC-ZrOx/Al2O3 coatings are deposited onto stainless steel (SS) substrates by the sputtering method for solar selective absorbing. The ZrC-ZrOx and Al2O3 layers work as an absorptance layer and an antireflectance layer, respectively. The substrate temperature has an important effect on the optical properties of the coating. With a high substrate temperature (300 °C), the SS/ZrC-ZrOx/Al2O3 coatings exhibit a relatively high absorptance of 0.92 and a relatively low emittance of 0.12. The composition, structure, optical properties and surface morphology of the coatings are characterized using SEM, EDS, XPS, Raman, UV-vis-NIR spectrophotometry and Fourier transform infrared spectroscopy. Detailed failure analysis of the SS/ZrC-ZrOx/Al2O3 coatings in vacuum and air is conducted.