Cu doped YInO3-ZnO green colored NIR reflective pigments: Synthesis and application in PMMA based cool-roof coatings

A series of Cu modified YInO3-ZnO green colored NIR reflective pigments was synthesized by sol-gel route. The dried gel precursor was calcined at different temperatures for 2 h (550 ◦C, 650 ◦C, 750 ◦C, 800 ◦C, and 850 ◦C), observing the formation of greenish pigments. The calcined pigments were characterized by thermogravimetry (TGA), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD) to investigate the physio-chemical and structural properties. The synthesized pigments showed near-infrared (NIR) reflectance ability and a green color attributed to the formation of Cu-substituted cubic and hexagonal YInO3 structures. The pigments were embedded in PMMA based to assess their potential to develop cool roofs coatings. The pigments demonstrated slightly reduced NIR reflectance when embedded in the polymeric paste. The thermal properties were assessed by exposing the coatings under a xenon arc lamp to measure the heating up of the coatings containing the various pigments.