Structural and Optical Properties of Several Iron Manganese Oxides to Prepare Thin Films as Solar Selective Absorbers
Abstract
In this work, the behavior of the mixture to form manganese iron oxides used as pigments for application in solar absorbers is investigated. Polished aluminum as substrate was covered with mixed Fe:Mn oxide by the impregnation method. After drying the thin films, the samples were submitted to different heat treatment temperatures. Chemical structure and optical properties were respectively evaluated using XRD and UV-Vis- IR spectrophotometry technique. The evolution of different structural phases during the addition of manganese ions process is discussed with Rietveld refinement of the X-ray diffraction. The results indicated a phase mixture of the two oxides for concentrations x = 0.87, 0.5 and a solid solution x = 0.93, 0.35, however the best selectivity values were obtained in the sample x = 0.35, indicating the addition of manganese is crucial for the pigment applied to solar applications substrate.The thin film profilometry let us to evaluate thin film thickness and the surface roughness. Finally, the effects of mixed oxides chemical composition on the solar selectivity (α / ε), will be discussed.
Keywords
Selective coatings, Hematite, Absorptance, Emittance, Rietveld method.