Exploration of Near-Infrared-Reflecting Zn_0.5M_0.5Fe₂O₄ Pigment for Sustainable Coatings by Transition Metal Substitutions and a Modifier

Abstract

Zinc ferrite pigments have emerged as potential candidates for enabling technology for large-scale energy-saving applications, which are safer, more accessible, and less damaging to the environment when compared to similar rare-earth-based colorants. Introducing transition metals into the ZnFe2O4 host lattice may distort the normally ordered lattice. A mineralizer was employed to further tune the color and infrared (IR)-reflective properties. NaCl lowered the crystallization temperature of the spinel zinc ferrite phase owing to its facilitation of ionic diffusion in solid-state reactions. Using a mineralizer promoted the generation of regular pigment particles to further enhance the optical property, leading to a low-cost, effective green strategy for heat mitigation. The acrylic coating of the pigment over the concrete substrate demonstrated good color consistency and near infrared (NIR) reflectivity (temperature shielding character). The surface temperature difference between the coated and uncoated acrylic binder-based mineralizer-added zinc ferrite was 16.4 °C. Since the synthesized zinc ferrite-based pigments have chemical stability and good NIR reflectivity and color characteristics, they have potential application for exterior energy-saving coatings.