Near Infrared Reflectance of the Doped Cr2O3 Pigment

Fe, Ti and Al-Ti binary-doped Cr2O3 pigments were prepared by solid-phase synthesis process. The phase structure, visible / near-infrared reflectance (NIR), color parameters were tested and characterized by X-ray diffraction (XRD), UV/VIS/NIR spectroscopy, Color CIE Chromaticity analysis software. The correlation between NIR reflectance, color and pigment structure features of doped Cr2O3 pigments was initially discussed. The results showed that all doped Cr2O3 had a single-phase corundum structure. However their grain sizes varied with doped elements relative to the undoped Cr2O3. It was found that the NIR of doped Cr2O3 decreased with adulteration of Fe but increased significantly with adulteration of Ti. For Al/Ti binary-doped Cr2O3 pigment with composition of 3.4wt% Al(OH)3 and 1.07wt% TiO2, the average reflectance in the wavelengths ranging from 700-2500 nm and maximum reflectance at 2500nm were 87.5% and 99%, respectively. The significant NIR enhancement of Ti-doped Cr2O3 was attributed to its larger grain size and change of Cr3+ local electronic environment.