Near Infrared Reflectance of the Doped Cr_2O_3 Pigment

Fe,Ti and Al-Ti binary-doped Cr_2O_3 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 Cr_2O_3 pigments was initially discussed.The results showed that all doped Cr_2O_3 had a single-phase corundum structure.However their grain sizes varied with doped elements relative to the undoped Cr_2O_3.It was found that the NIR of doped Cr_2O_3 decreased with adulteration of Fe but increased significantly with adulteration of Ti.For Al/Ti binary-doped Cr_2O_3 pigment with composition of 3.4wt%Al(OH)_3 and 1.07wt%TiO_2,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 Cr_2O_3 was attributed to its larger grain size and change of Cr~(3+) local electronic environment.