Preparation, characterization, and properties of a Ba2+–Sm3+ co-doped γ-Ce2S3 red pigment

Abstract

In this study, Ba2+–Sm3+ co-doped γ-Ce2S3 (abbreviated as γ-[Ba,Sm]-Ce2S3) red pigments were synthesized by the coprecipitation method with a composition of n(Ba)/n(Ce1−xSmx) = 0.1(molar ratio, x = 0, 0.01, 0.03, 0.05, and 0.10 mol). The corresponding vulcanized products, γ-[Ba,Sm]-Ce2S3 red pigments (abbreviated as S.Smx), were prepared using CS2 as a sulfur source at 850 °C for 150 min. The effect of the Sm3+ doping content on the phase composition, chromaticity, and thermal stability of Ba2+–Sm3+ co-doped γ-Ce2S3 was systematically investigated by FE-SEM, EDS, XRD, Raman spectroscopy, HR-TEM, XPS, CIELAB colorimetry, and TG-DTA. The results show that a pure γ phase can be obtained for S.Smx, when x is varied from 0 to 0.10 mol at 850 °C. With an increase in the Sm3+ content, the band gap of γ-[Ba,Sm]-Ce2S3 increased from 2.12 to 2.14 eV, which resulted in a color change from red to red-orange. The chromaticity value of the pigments increased from L∗ = 31.84, a∗ = 30.95, b∗ = 23.63, and C∗ = 38.94 (S.Sm0.00) to L∗ = 34.63, a∗ = 35.36, b∗ = 38.88, C∗ = 52.55 (S.Sm0.01), which indicates that Ba2+–Sm3+ co-doping can effectively increase the chromaticity value. The S.Sm0.01 sample still exhibited a pure γ-phase and showed excellent red color (L∗ = 33.18, a∗ = 33.74, b∗ = 36.69, and C∗ = 49.84) after the heat treatment at 400 °C for 10 min in air, which indicated that Ba2+–Sm3+ co-doping successfully increased the thermal stability of the S.Sm0.01 red pigment. S.Sm0.01 has excellent chromaticity and good thermal stability, which expands the number of methods for preparing γ-Ce2S3 red pigment and shows a considerable market potential.