Eco-friendly Li_3InB_2O_6 based red pigments for various IR blocking cool coating applications

摘要

New red chromatic inorganic powder pigments were prepared by the introduction of Mn3+ in the host lattice of monoclinic Li3InB2O6. Substitution of Mn3+ ion in the indium site of host lattice changed the powder color from grey-white to (x = 0) red with (x = 0.08). The absorption spectra of the synthesized samples revealed that the development of red color occurred might be due to the crystal field splitting of Jahn-Teller distorted MnO6 octahedra. An attempt was also made to distort the crystal field around the Mn3+ via the doping of larger alkali metal ions into the Li sites of Li3In0.92Mn0.08B2O6 host lattice. This substitution effect altered absorption properties translated in enhancing the red chromaticity for Li2.95Na0.05In0.92Mn0.08B2O6 with a CIE redness value of (a* = 29.5). Furthermore, the developed pigments and the substrate material coated with them showed good NIR solar reflectance in the range of 700-2500 nm. Finally, the thermal shielding performance of the synthesized pigments was evaluated for their usage as building roof coatings.