Environmentally friendly orange pigments based on hexagonal perovskite-type compounds and their high NIR reflectivity

Novel environmentally friendly inorganic orange pigments based on the hexagonal perovskite-type pigment Sr4Mn2(Cu1-xZnx)O9 (0 ≤ x ≤ 1) were synthesized and their optical and color properties were determined. Using Zn2+ doping (x = 0.5), the optical absorption caused by a ligand-metal charge transfer transition was reduced due to anisotropic lattice distortion, while the optical absorption corresponding to the d-d transition of Cu2+ was clearly observed at 670 nm. As a result, the Sr4Mn2(Cu0.5Zn0.5)O9 sample possessed a brilliant orange color with L*, a*, b*, C, and H° values of 64.0, +19.8, +52.3, 55.9, and 69.3, respectively. In addition, the Sr4Mn2(Cu0.5Zn0.5)O9 orange pigment also possessed outstanding NIR reflectance compared with the commercially available bayferrox orange 960, indicating the potential of this new pigment for use as an energy-saving material.