A significant amount of heat is absorbed by conduction at the surface of a material exposed to sunlight. Urban buildings consume enormous amounts of energy, including electrical power, especially from air conditioners used to keep building interiors cool. One way to decrease the increased energy demand for air conditioning is to use cooler roofs and walls. Cooler roofs will reflect solar radiation, especially NIR radiation, and reduce the amount of energy absorbed by the building. To this end, NIR-reflecting inorganic pigments, known as cool pigments, used in coatings applied to roofing products such as metal panels or tiles are important materials that not only provide this property but also provide the required aesthetic appearance.

In this work, inorganic, non-toxic pigments based on the Fe(III)-doped perovskite YAlO₃ structure with high near-infrared (NIR) reflectance were synthesized by a modified Pechini method at 1200°C. A complete solid solution in the YAl_1-xFe_xO₃ system (x=0, 0.25, 0.5, 0.6, 0.75, 1) was prepared, obtaining a wide range of colourations from yellow to red, depending on the iron content. The colour of these compounds was studied by UV-Vis spectroscopy and colorimetry.

Good pigment stability was achieved in a high-temperature commercial glaze, used in the ceramic industry to colour glazes on tiles. The pieces coating with the pigmented glazes reaches NIR solar reflectance values between 43-32%. The temperature protection studies carried out, with the unpigmented glaze and the pigmented glazes with the compositions YAl_0.75Fe_0.25O₃ and YFeO₃, conclude that as a roof coating, the pigmented samples reduce the temperature of a building by 5°C and 4°C, respectively, in comparison to the unpigmented glaze.

The results obtained in the thermal protection studies are important and indicate that these pigments can be excellent candidates for used in high-temperature applications such as colouring ceramic glazes at high temperatures, as well as cooling pigments in walls or roofs of buildings.