Synthesis and characterisation of SrY2−xCexO4 as environmentally friendly reddish-brown pigments

Abstract

Reddish-brown SrY_2−xCe_xO₄ (0 ≤ x ≤ 1.2) solid solutions were synthesized by a citrate sol–gel method as novel environmentally friendly inorganic pigments. The powders obtained were characterized by X-ray powder diffraction (XRD), UV-vis diffuse reflectance spectra and CIE L*a*b*Ch° chromatic coordinate measurements. All SrY_2−xCe_xO₄ (0 ≤ x ≤ 1.2) samples were obtained in a single-phase form and the lattice volume increased on increasing the Ce³⁺ concentration. The reddish-brown pigments exhibited optical absorption due to the 4f–5d allowed transition of Ce³⁺. The absorption bands observed in the wavelength region of 400 and 550 nm were due to the Ce³⁺ ions in the ideal octahedral Y³⁺ site and those in the longer wavelength region above 600 nm were attributed to the transition of Ce³⁺ in the distorted octahedral Y³⁺ site. The samples gradually became reddish on increasing the Ce³⁺ content. The most reddish colour was obtained in SrYCeO₄ (a* = +21.8).