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

Abstract

Reddish-brown SrY2-xCexO4 (0 ≤ ×. ≤ 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 SrY2-xCexO4 (0 ≤ ×. ≤ 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).