Optical property and thermal performance of hollow glass microsphere/BiOBr1-xIx composites as a novel colored near infrared reflective pigment

In this work, hollow glass microsphere/BiOBr1-xIx composites was synthesized as a series of novel colored near infrared reflective pigments. BiOBr1-xIx microflowers or microspheres were deposited on hollow glass microspheres using a simple chemical liquid deposition method. The morphologies and optical properties of the composite pigments were found to differ drastically by varying the molar ratio of I to Br. The color of the composite pigments was observed to turn from white to yellow, and then to red as the increased content of I. The band gap of the composites decreased from 2.87 to 1.87 eV with increasing I content. The near infrared solar reflectance of hollow glass microsphere/BiOBr1-xIx composite pigments was as high as 0.952. An approximately 9.4 degrees C decrease in outer surface temperature was obtained for the heat box coated with the composite pigments. Therefore, the synthesized composite pigments with tunable colors and high NIR reflectance have the potential to be applied as cool pigments in cool coatings to reduce the heat build-up.