Near-infrared reflective coatings based on red-brown Ce1-xPrxO2 pigments

Abstract

Red-brown Ce1-xPrxO2 pigments have high reflectance values over the entire NIR range, which recommend their use as NIR-reflective (cool) pigments. Ce0.99Pr0.01O2 pigment had the highest proportion of red and the lowest proportion of yellow (CIEL*/a*/b* = 60.1/19.7/13.1), corroborated with a total solar reflectance of 54.1 %. The pigments based on Ce1-xPrxO2 showed excellent behavior both in coloring an aqueous acrylic paint applied onto a metal substrate and a transparent glaze applied on a ceramic tile. The tile glazed with the Ce0.99Pr0.01O2 pigment had a significantly higher total solar reflectance (TSR = 45.0 %) than a commercial reference ceramic tile (TSR = 24.2 %), whilst the color of the two was comparable. In the case of metal substrates, the maximum temperature measured on the surface of the acrylic coating based on Ce1-xPrxO2 (54.0 °C) having a total solar reflectance of 51.4 %, was almost 10 °C lower than the temperature measured on the surface of the reference coating (63.7 °C), having a total solar reflectance of 35.7 %. These results demonstrate the extraordinary potential of Ce1-xPrxO2-based pigments to prevent overheating of metal/ceramic surfaces exposed to NIR radiation including, but not limited to, roofing applications.