A Tantalum diffusion barrier layer to improve the thermal stability of Al_xO_y/Pt/Al_xO_y multilayer solar absorber

摘要

The effect of a thin Tantalum layer on the thermal stability of Al_xO_y/Pt/Al_xO_y multilayered selective solar absorber coatings has been investigated. The resulting samples were annealed at different temperatures for different durations in air. These were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, Atomic force microscopy, Raman spectroscopy, UV-vis-NIR spectrophotometer and emissometer. The Cu/Ta/Al_xO_y/Pt/Al_xO_y multilayer solar absorber coatings were found to be thermally stable up to 700 ℃ in air for 2 h with good spectral selectivity (α/ε) of 0.932/0.10. At 800 ℃, the spectral selectivity decreased to 0.870/0.12, which is attributed to the diffusion of Cu and formation of CuO phase. The formation of CuO phase was confirmed by X-rays diffraction, energy dispersive spectroscopy and Raman spectroscopy. Long term thermal stability study showed that the coatings were thermally stable in air up to ～550 ℃ for about 24 h.