A New Series of Environment-Friendly Reddish Inorganic Pigments Based on AFeO3 (A = Ln, Y) with High NIR Solar Reflectance

Environment-friendly pigments based on AFeO3 (A = La, Pr, Nd, Sm, Gd, Tb, Y or Yb) with high near-infrared (NIR) reflectance were synthesised by a coprecipitation method at 1200 °C. The Rietveld refinement analysis showed single-phase orthorhombic perovskite for all compositions. All pigments, which showed reddish hues, offered good colour stability after mixing these pigments in powder form with siloxane transparent paint and two different glazes. The powder–paint mixtures produced with GdFeO3, TbFeO3 and YFeO3 pigments have the highest NIR solar reflectance, reaching values of R = 50%. The temperature shielding studies conducted using TbFeO3 pigment–paint mixture for a roof coating yielded a reduction of 3.2 °C in comparison to a commercial pigment. Moreover, the glazes that were pigmented using GdFeO3, TbFeO3 and YFeO3 compositions also presented the most intense reddish colours. A study of the thermal and chemical stability of the pigment with the highest NIR solar reflectance showed good stability in both cases. The reddish pigments that were prepared can therefore be good candidates for use in different applications such as cool pigments or pigments for ceramic glazes at high temperatures.