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.
We systematically study the crystal structure, magnetism and cryogenic magnetocaloric effect (MCE) in heavy rare-earth RE 6 MoO 12 ( RE = Tb, Dy, Ho, and Er) compounds. All RE 6 MoO 12 compounds belong to a cubic structure (space group: F m 3 − m ). Meanwhile, magnetic measurements illustrate that RE 6 MoO 12 compounds exhibit an antiferromagnetic (AFM) phase transition. It is proved by the slope of the basic Arrott-plots that all compounds undergo second-order magnetic phase transition (SOMT). In addition, under the applied magnetic change ΔH = 7 T, the maximum magnetic entropy change (-∆ S M max ) near Néel temperature ( T N ) is evaluated to be 12.9, 20.7, 21.1, and 21.2 J/kg K, and relative cooling power ( RCP ) is evaluated to be 308.3, 473.9, 506.2, and 381.4 J/kg for Tb 6 MoO 12 , Dy 6 MoO 12 , Ho 6 MoO 12 , and Er 6 MoO 12 , respectively. Consequently, our study underscores the magnetism and magnetocaloric effect properties exhibited by heavy rare-earth RE 6 MoO 12 compounds family, positioning them as a potential magnetic refrigerant in the field of low-temperature magnetic refrigeration.
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