Thermal stability of multilayered Pt-Al2O3 nanocoatings for high temperature CSP systems

Abstract

This contribution reports on the effect of thermal annealing on sputtered Pt–Al(sub2)O(sub3) multilayered selective solar absorber coatings deposited onto stainless steel substrates with a Mo IR reflecting buffer layer. The Pt–Al(sub2)O(sub3) cermet nanocoatings were annealed at different temperatures for different durations in vacuum. The spectral selectivity of the optimised Pt–Al(sub2)O(sub3) was found to be thermally stable up to 900 °C in vacuum for 2 h with solar absorptance of 0.944 and thermal emittance of 0.11. At 1000 °C, its spectral selectivity decreased significantly to 0.892/0.13, which is attributed to the inter-diffusion between the layers, and formation of -Fe(sub3)Mo(sub3)C phase. Annealing the Pt–Al(sub2)O(sub3) nanocoatings for long term showed that the cermet nanocoatings were thermally stable up to 800 °C in vacuum for 24 h having spectral selectivity of 0.938/0.10.