New red pigments based on Li3AlMnO5 for NIR reflective cool coatings. Issue 21 (1st November 2021)

• Record Type: Journal Article
• Authors: Divya, S.; Das, Subrata
• Is Part Of: Ceramics international. Volume 47:Issue 21(2021)
• Page Start: 30381
• Page End: 30390
• Publication Date: 2021-11-01
• Subjects: Red pigment -- MnIVO6 octahedra -- NIR reflectance -- Cool coating; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2021.07.218
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: The exploration of new red pigments based on transition elements is of great practical value in the field of inorganic pigments, since the red coloured pigments have unique applications in paints, ceramic tiles, cosmetics, etc. Here we mainly reported a new class of eco-friendly red pigments based on substituted Li3 AlMnO5 (LAMO) and briefly state about the other rock salt layered structure Li3 GaMnO5 (LGMO). The solid-state synthesized powders were crystallized to monoclinic structure having Mn IV (1) 2b and Mn IV (2) 4g site. The absorption bands in the synthesized samples mainly arises due to the octahedrally coordinated Mn IV O6 in the 4g site. Among the synthesized samples, LAMO: 0.10Ti 4+ showed exemplary chromatic properties. The doping of tetravalent Ti 4+ ions in the Mn 4+ sites altered the Mn IV (2)O6 bond lengths and increased the crystal field around the absorption band attributed to the 4 A2g → 4 T2g transitions. The ball milled LAMO: 0.10Ti 4+ shows the a* value of 40.05, which is higher than that of the commercially available red iron oxide pigments (a* = 28.9). Meanwhile, the brighter red powder LAMO: 0.10Ti 4+ demonstrated appreciable thermal and chemical stability. From the thermal evaluating study, we observed that, LAMO: 0.10Ti 4+ pigment coated roof panels showed a temperature difference of (3.2 °C) compared to the bare roof panel (3.7 °C). We estimated the coating's performance of the LAMO: 0.10Ti 4+ in concrete block, metal plate and ceramic tile. In these substrates, the pigment possesses distinctly elevated NIR‐reflectance, which makes these materials worthwhile for cool coating applications.