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

This contribution reports on the effect of thermal annealing on sputtered Pt-Al2O3 multilayered selective solar absorber coatings deposited onto stainless steel substrates with a Mo IR reflecting buffer layer. The Pt-Al2O3 cermet nanocoatings were annealed at different temperatures for different durations in vacuum. The spectral selectivity of the optimised Pt-Al2O3 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 η-Fe3Mo3C phase. Annealing the Pt-Al2O3 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.