High-temperature optical properties and stability of selective absorbers based on quasicrystalline AlCuFe

Abstract

Solar selective absorbers based on AlCuFe thin films and a cermet of AlCuFe particles embedded in an Al2O3-matrix were produced by sputter deposition. Si-wafers coated with copper layers were used as substrates. According to X-ray diffraction and high-resolution transmission electron microscopy (HRTEM), the AlCuFe layers are quasicrystalline or consist of a mixture of quasicrystalline and crystalline phases. Reflectance of the selective absorber based on the AlCuFe cermet was measured in the wavelength region 400–1700nm at temperatures up to 395°C with the absorber held in high vacuum. Changes of reflectance with temperature can mostly be assigned to changes of the optical properties of the copper layer. Stability at high temperatures in air was studied by heating the absorbers to 400°C for different time intervals up to 450h. Only small changes in optical properties were found during this heat treatment, while rapid degradation within about 40 h occured at 500°C. According to elastic recoil detection analysis (ERDA), samples degraded by diffusion of copper and silicon to the surface and their subsequent oxidation.