Synthesis and characterization of aluminum-based γ-Ce2S3 composite red pigments by microemulsion method

Aluminum-based γ-Ce2S3 composite red pigments were prepared by sulfurization and calcination of precursors, which were synthesized by microemulsion method. As initial materials, CeCl3·7H2O, Nd(NO3)3·6H2O, Al(NO3)3·9H2O, and Mg(NO3)2·6H2O were used, and CS2 and B2O3 were used as sulfur source and additive, respectively. The precursors were synthesized in ambient condition, followed by sulfurizing treatment at 900 °C for 300 min and heat treatment at 1200 °C for 60 min in an inert atmosphere. Effect of sulfurization condition on the phase composition of the pigment was observed. Furthermore, the morphology, thermal stability, and chromaticity of the pigments having different Ce/Nd/Al/Mg molar ratios and pH values were investigated. The results indicated that the obtained γ-Ce2S3 pigment was composed of two kinds of aluminum-based materials (corundum and spinel). The pigments exhibited bright red color, CIE coordination (corundum-based: L* = 42.83, a* = 34.22, b* = 30.59; spinel-based: L* = 38.05, a* = 34.27, b* = 25.34) and better thermal stabilities than the pure pigments, with decomposition temperatures ≤ 479.5 °C for the corundum-based pigment and ≤474.5 °C for the spinel-based pigment. Acid picking test results indicated that the pigments were composed of uncoated γ-Ce2S3 particles and aluminum-based coated γ-Ce2S3 particles. The residues obtained from both aluminum-based coated pigments after acid picking maintained the red hue in air at 800 °C.