Influence of composition on near infrared reflectance properties of M-doped Cr<sub>2</sub>O<sub>3</sub> (M=Ti,V) green pigments

Abstract

Ti-Al-V-doped Cr2O3 green pigments could present a higher near-infrared (NIR) reflectance compared to pure Cr2O3. The amount of Ti and V introduced in the Cr2O3 matrix has been systematically varied respectively, in order to evaluate the effects of Ti and V contents on the NIR properties of the doped Cr2O3. For comparison, experimental reflectance measurements and mean-NIR reflectance (780–2000 nm) of samples are given. The results reveal significant variations in the NIR region as a function of nominal composition for both Ti-doped Cr2O3 and V-doped Cr2O3. Moreover, the NIR reflectance of a Ti-Al-V-doped Cr2O3 pigment sample was measured. It has been found that it exhibits lower NIR reflectance compared to that reported in previous study. The correlations between electronic structural and spectroscopic features are discussed. For the Ti-doped Cr2O3 samples, the decrease of free carriers and the electronic transitions between defect energy levels within the band gap and the conduction band, could be responsible for the variable NIR reflectance. However, for V-doped Cr2O3, apart from light absorptions of free carriers, there are new light absorption peaks range from 1190 to 2000 nm, resulting in the variations of the NIR reflectance.