Color Tunable Pigments with High NIR Reflectance in Terbium-Doped Cerate Systems for Sustainable Energy Saving Applications

Abstract

Color tunable pigments from yellow to red hues were developed in Tb-doped A2CeO4 (A = Sr and Ba) system by the conventional ceramic route. The developed pigments were analyzed for their phase purity, chemical oxidation state, elemental analysis, morphology, and optical properties by various advanced techniques. The Ba substitution in Sr2−xCe0.6Tb0.4O4 gently shifts the absorption edge to higher wavelengths producing bright yellows to reddish orange colors whereas the Tb substitution in Ba2Ce1−xTbxO4 allows abrupt shift in the absorption edge to longer wavelengths leading to intense red hues. The chemical oxidation state analysis indicates the modifications of Tb3+ concentrations in both the environments due to metal to metal charge transfer transitions induced by lattice expansion. Typically the compositions SrBaCe0.6Tb0.4O4 (yellow; b* = 75.36, R = 91%) and Ba2Ce0.4Tb0.6O4 (red; a* = 30.09, R = 89%) exhibit brilliant coloristic and reflectance properties. The applicability studies revealed good coloring performance in the polymer matrix and on concrete slab with high solar reflectance. Further, the pigments are proven to be weather resistant in acid/alkali/moisture atmospheres with good thermal stability. These color characteristics with high solar reflectance of sustainable and ecofriendly compositions make them promising colorants for exterior coating formulations to mitigate the cooling energy consumption.