The influence of Mn/N-codoping on the thermal performance of ZnAl2O4 as high near-infrared reflective inorganic pigment

In this study, a series of Mn-doped ZnAl 2 O 4 and Mn/N co-doped ZnAl 2 O 4 were synthesized by the sol-gel method. Comprehensive analyses of compounds and coatings were carried out to characterize results. Several colored inorganic samples are studied, including their ability as cool pigments. The results show that prepared compounds exhibit different spectral reflectance extents in the near-infrared region despite their structural similarities, which illustrates the near-infrared reflective properties are dependent on the doping elements. The different doping has an effect on the thermal performance, especially in the visible and near-infrared regions. The substitution of Mn/N changed the color from white to flesh color, while the band gap varies in the range from 3.64 ev to 2.90 ev. Furthermore, the Mn/N co-doped ZnAl 2 O 4 compounds exhibit high near-infrared reflectance (>50%) and the near-infrared solar reflectance (>48.83%) in the range of 700–2500 nm. We also evaluated the thermal performance of Mn/N co-doped ZnAl 2 O 4 and conventional pigment coatings of the same color by testing the temperature distribution at different parts of the aluminum plates. It indicates that the prepared compounds have the potential to be applied to energy savings as novel color pigments.