Preparation and properties of SiO2 wrapped γ-(CeLa)2S3 orange-red pigment by Stober method

γ-(CeLa)₂S₃ is a newly developed rare earth inorganic orange-red pigment characterized by non-toxicity, bright coloration, and high weather resistance, though its thermal stability is limited to 350 °C. The Stober method provides an effective approach for enhancing its thermal resistance by applying a high-temperature-resistant coating to the pigment surface. In this study, commercially available orange-red γ-(CeLa)₂S₃ pigment was selected for investigation. The influence of solid content on the coating performance was examined, using CTAB as the dispersing agent, TEOS as the silicon source, anhydrous ethanol and pure water as co-solvents, and NH₃·H₂O to adjust the solution pH. Results indicate that when the solid content reaches 100 g, and the ethanol-water ratio and total volume remain constant, the coated pigment demonstrates superior thermal and acid resistance. The pigment retains its orange-red color (L∗ = 45.40, a∗ = 35.21, b∗ = 47.80) after being calcined at 450 °C and exhibits no significant color alteration following 12 h immersion in 1.0 M hydrochloric acid.