Yellow rare earth sulfide powders with near-infrared reflectance and spectral modulation for energy-saving applications

Radiative cooling pigments offer new opportunities for sustainable carbon neutrality as zero-energy and zero-pollution functional materials. However, it is a challenge to prepare inorganic yellow pigments simultaneously with environmentally friendly, high color value, and weather resistance. In this study, a series of alkali metal-doped γ-Sm 2 S 3 yellow pigments with near-infrared reflectance were synthesized. The doping of alkali metal ions reduced synthesis temperature of Sm 2 S 3 from 1300°C to 1000°C. The change in energy band structure induced by alkali metal doping allows the products to exhibit modifiable colors. Typical γ-[Na]-Sm 2 S 3 pigment powders have a high near-infrared reflectance and impressive colors ( b* = 78.6, C* = 77.6). Furthermore, colored films made by prepared yellow powders with polyvinylidene fluoride in certain ratios had high near-infrared reflectance and excellent environmental weathering, resulting in an effective cooling of 4–8°C in outdoor experiments. This work expands the range of options for energy-efficient building and yellow colorant.