Ce doped (Y, Yb)3Al5O12 yellow cool pigment with high solar reflectance and enhanced colour performance

The high solar reflectance and good colour performance are requisite for the practical application of the colour-cool pigment. In this work, Ce-doped Yb 3 Al 5 O 12 and (Y, Yb) 3 Al 5 O 12 ceramic pigments were prepared by the sol-gel method. Both Ce 3+ and Ce 4+ ions coexist in the doped pigments. Due to the 4f→5d electron transition of Ce 3+ , the Ce-doped pigments have a selective absorption at around 400–520 nm, which is responsible for the yellow hue. The content of the Ce 3+ ion determines the colour performance of the pigment. The size effect from the smaller Yb 3+ ion results in an increased content of Ce 3+ in the Ce-doped pigments, leading to an improved colour performance. The incorporation of Y 3+ ion can effectively decrease the absorption at 975 nm, thereby enhancing the solar reflectance to 80.6 %, while maintaining good colour performance (Yb 0.7 Y 2.1 Ce 0.2 Al 5 O 12 , L*  = 91.40, a*  = -4.89, b*  = 45.33). In a simulation experiment, the ceramic glaze coating based on the prepared pigment showed a temperature reduction of 5.2 °C compared to the commercial yellow pigment ceramic coating .