Color Optimization of Yellow Cool Pigments via Defect Engineering: Mo and Ce Co-doped Y2Zr2O7 with High Near-Infrared Reflectance

A series of molybdenum (Mo) and cerium (Ce) co-doped Y 2 Zr 2 O 7 inorganic cool pigments were synthesized via a high-temperature solid-state reaction method. Substitution of Zr by Mo introduces interstitial oxygen into the lattice, leading to lattice expansion while enhancing the near-infrared reflectance of the pigments. Mo coexists in the form of Mo 6+ and Mo 5+ ions, with the yellow coloration primarily originating from Mo 5+ . The lattice expansion induced by the incorporation of larger Ce ions suppresses the formation of interstitial oxygen, thereby promoting an increase in Mo 5+ content, which results in a higher b* value while maintaining high near-infrared reflectance. The optimized composition (Y 1.55 Ce 0.45 Zr 1 Ce 0.65 Mo 0.35 O 7 ) exhibits the following chromatic parameters: L* = 88.26, a* = -3.19, b* = 55.15, and R NIR =93.68%. Furthermore, the simulation experiment revealed that the surface temperature of the coating based on the as-prepared pigment is 16.3 °C lower than that of the cement coating and 11.4 °C lower than that of the commercial iron yellow coating, demonstrating excellent solar reflective performance.