A novel rare-earth high-entropy RE6MoO12 with high near-infrared reflectance as a promising inorganic “cool pigment”

Abstract

Inorganic “cool pigments” exhibit excellent application potential in double-carbon strategies and energy savings. High-entropy RE 6 MoO 12 inorganic “cool pigments” with a disordered defect-fluorite-type structure namely, (La 0.25 Y 0.25 Er 0.25 Ho 0.25 ) 6 MoO 12 , (Nd 0.25 Y 0.25 Er 0.25 Ho 0.25 ) 6 MoO 12 and (Tb 0.25 Y 0.25 Er 0.25 Gd 0.25 ) 6 MoO 12 , were prepared through a solid-state reaction for the first time. The optical properties, color performance and thermal insulation of these materials were characterized. These pigments exhibited a high near-infrared (NIR) reflectance of 81–98%. The average NIR reflectance of the (La 0.25 Y 0.25 Er 0.25 Ho 0.25 ) 6 MoO 12 (97.31%) and (Nd 0.25 Y 0.25 Er 0.25 Ho 0.25 ) 6 MoO 12 (92.50%) pigments were greater than 90%. The high-entropy RE 6 MoO 12 pigments possessed better chemical stabilities in acid-alkali tests than single components. In addition, the thermal conductivity of the fully dense HE-RE 6 MoO 12 pigments was 1.05–1.16 W m −1 K −1 at room temperature, which is approximately 40–50% lower than that of RE 6 MoO 12 . The designed HE-RE 6 MoO 12 pigments showed three colors: yellow, green and brownish red. In conclusion, the multicolored high-entropy RE 6 MoO 12 pigments possessed good potential for increasing NIR solar energy reflection, which can meet the needs of “cool pigments” performance upgrades.