Rare‐Earth Y‐Based Molybdate High Near‐Infrared Reflective Orange Pigment Based on Bi Doping

In this article, a series of bismuth (Bi)‐doped rare‐earth molybdate orange pigments with near infrared (NIR) properties were synthesized by high temperature solid phase reaction at 1400°C with the general formula of Y 4−x Bi x MoO 9 . The prepared pigments were characterized by analytical techniques such as X‐ray diffraction (XRD), scanning electron microscopy (SEM), CIE 1976 color space system, and ultraviolet‐visible/near‐infrared spectroscopy (UV‐Vis/NIR). After doping Bi 2 O 3 into Y 4 MoO 9 , its color changes from yellow to red and finally to orange. All the doped samples belong to the monoclinic crystal system. All pigment samples have an NIR reflectance (R%) of over 97% at 1100 nm. In the study of acid and alkali resistance, the color difference value Δ E * of the pigment before and after soaking in acidic and alkaline solutions is less than 2, indicating its good chemical stability. In the coating simulation investigation, the indoor air temperature difference between the house model coated with synthetic pigments and the house model coated with commercial pigments reaches 8.2°C, indicating that Y 4‐x Bi x MoO 9 pigments had good isolation effect and application prospects as a cool pigment.