Colour tunable cool pigments based on TiZn2O4 inverse spinels

Abstract

A new class of near-infrared (NIR) reflecting yellow and orange cool pigments based on TiZn₂O₄ inverse spinels were synthesized. The colour tuning in pure TiZn₂O₄ was made possible by the substitution of octahedral Zn²⁺ ions by Cu²⁺ and Fe³⁺ ions separately. By the incorporation of Cu²⁺ and Fe³⁺ ions into the inverse spinel lattice in varying amounts, a series of pigment compositions having colours ranging from greenish-yellow to reddish-brown was obtained. The developed pigments exhibited moderate to high NIR reflectance ranging from 47.61 to 87.81%. The TiZn₂O₄ based NIR reflecting pigment provided an interior 4.8 °C cooler than an uncoated roofed interior. Cu²⁺ and Fe³⁺ doped TiZn₂O₄ systems were found to be highly stable and eco-friendly cool pigment candidates capable of achieving better thermal conditioning and impressive energy conservation.