Development of High NIR‐Reflective Red Li<sub>2</sub>MnO<sub>3</sub> Pigments
Georg Gramm, Gerda Fuhrmann, Fabian Zimmerhofer, Martin Wieser, Hubert Huppertz
Abstract
In this work, the development of a novel class of eco‐friendly red pigments based on doped Li 2 MnO 3 is reported. These new compounds offer red color values of a * > 34, which are recognizably higher than the red value provided by the commonly used red pigment iron oxide Bayferrox 4130. However, the real outstanding attribute of these novel substances is their strikingly high NIR‐reflectance that gives promise for a new class of materials for the practical utilization as cool pigments in building components and ceramics. We have synthesized the inorganic pigments by conventional solid‐state reactions at 900 °C and subsequently carried out the structural characterizations by X‐ray powder diffraction (XRPD) and Rietveld analysis. We recorded the diffuse reflectance spectra of the obtained powders and determined the color properties by means of CIE L*a*b * coordinates. Finally, we measured the NIR reflectance and calculated the NIR solar reflection of these compounds affording values above 85 % in the range from 700 to 2500 nm.