Controllable near-infrared reflectivity and infrared emissivity with substitutional iron-doped orthorhombic YMnO3 coatings

Abstract

High near-infrared (NIR) reflectivity and infrared emissivity are desired in cooling pigments used in exterior coating of buildings. More importantly, controllable infrared emission and NIR reflectivity are needed for the next generation buildings. In this work, tunable NIR reflectivity and infrared emissivity were realized with substitutional iron-doped orthorhombic YMnO3 for the first time. The iron-doped orthorhombic YMnO3 were successfully synthesized by using a facile molten salt synthesis (MSS) method under low temperature and normal pressure. The effect of substitutional iron-doping on the microstructure, NIR reflectance and infrared radiation characteristics of orthorhombic YMnO3 were investigated. The results showed that substitutional doping of Fe ions was an effective method to control the NIR reflectivity and infrared emissivity. The emissivity of Fe ion-substituted pigmented coatings in 8-14 µm waveband (atmospheric window) was obviously increased due to the lattice distortion. Moreover, the increased amount of Mn3+-Mn4+ ions pairs in the pigments with moderate Fe ions content led to the strengthened absorption of free carrier and the further increased infrared emissivity of the pigmented coatings. Furthermore, the pigmented coatings with higher Fe ions content had enhanced reflectivity in the 1500-2200 nm waveband, since the pigments possessed well-grown and plate-shape particles. The results in this work indicated that the Fe ion-substituted orthorhombic YMnO3 pigments had promising application prospects in energy conservation of buildings by utilizing NIR shielding as well as space cooling.