Investigation on multifunctional binary oxides for near-infrared (NIR) reflective pigment applications

In this work, we have investigated the solar reflective and color pigmentation effectiveness of some multifunctional binary oxides, Nb 2 O 5 , Ta 2 O 5 , Gd 2 O 3 , Dy 2 O 3 , La 2 O 3 , Sb 2 O 3 , Cr 2 O 3 , Y 2 O 3 , SnO 2 , and MnO 2 with the aid of XRD and diffuse reflectance spectroscopy (DRS) techniques. We have also reviewed the recent studies in NIR pigments of multifunctional oxides. From the obtained NIR reflectance values, we note that Gd 2 O 3 , Sb 2 O 3 , Ta 2 O 5 , Nb 2 O 5 , and Y 2 O 3 showed interesting features on NIR reflectance on both the solar reflective (750–1350 nm) and color pigmentation region (1350–2500 nm). The oxides like SnO 2 and La 2 O 3 demonstrate relatively high solar reflective pigmentation (750–1350 nm) features than color pigmentation. MnO 2 and Cr 2 O 3 show low NIR reflectance both in solar and color pigmentation regions as compared to other types of oxides investigated in the present work. Among the different investigated oxides, Nb 2 O 5 exhibits a relatively high NIR reflectance value (~ 85%) in the NIR region (750–2500 nm). On the other hand, the MnO 2 powder reveals the lowest NIR reflectance value (15–20%) in the NIR region. The UV–visible absorbance spectra and their energy bandgap of the different oxides have also been compared.