Estimating thermal performance of cool coatings colored with high near-infrared reflective inorganic pigments: Iron doped La2Mo2O7 compounds

• Fe doped La2Mo2O9 were synthesized and corresponding pigmented coatings were prepared.
• The pigments are brilliant yellow and have high near-infrared reflectance of 71–93%.
• Prepared coatings have higher solar reflectance of 61–75% compared with common coating.
• Indoor air temperature difference of boxes in simulation test reaches more than 4.5 °C.
• The designed coatings can well serve as cool colored coatings for buildings.

The paper estimates the thermal performance of cool coatings colored with a series of novel, environmentally benign and high near-infrared reflective inorganic pigments. Nanocrystalline La2Mo2−xFexO9 (x = 0, 0.03, 0.05, 0.08, 0.10) pigments were synthesized with acrylamide gel technique. The substitution of Fe3+ for Mo6+ in La2Mo2O7 results in the color change from white to brilliant yellow. Fe3+ doped pigments have high near-infrared spectral reflectance of 71–93%. The thermal performance of corresponding pigmented coatings was estimated. Results demonstrate that the designed colored coatings possess high spectral reflectance close to that of corresponding pigments in the short near-infrared spectral range, and high solar reflectance of 61–75%, far superior to traditionally available building roofing materials of the same color. The indoor air temperature difference reaches more than 4.5 °C in the simulated experiment, in which the boxes were covered with designed cool coating and traditional coating on their tops, exhibiting its pronounced thermal performance.