Promoting thermal stability and acid resistance of rare earth sulfide powders by coating ZnO and SiO2 double shells

• Published in: Journal of the American Ceramic Society 2024-05, Vol.107 (5), p.3415-3423
• Main Authors: Li, Renhan, Bai, Gongxun, Zhang, Hongbin, Song, Enhai, Zhang, Jiasong, Li, Denghao, Zhang, Junjie, Xu, Shiqing
• Format: Article
• Language: English
• Subjects: Acid resistance; coating; Coloring; Earth; Iron sulfides; Oxide coatings; rare earth sulfide; Silicon dioxide; SiO2; stability; Thermal resistance; Thermal stability; Zinc coatings; Zinc oxide; ZnO nano‐layer
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.19617

As an environment‐friendly powder with good coloring performance, rare earth sulfide is one kind of the important choices to replace cadmium and lead colorants. In particular, γ‐Ce2S3 belongs to rare earth sesquisulfide, which has a bright red color. However, the uncoated γ‐Ce2S3 is easy to decompose and release H2S in a humid or acidic environment, and its air thermal stability is limited to 350°C. In this work, γ‐Ce2S3 powders coated with zinc oxide were prepared by heterogeneous precipitation method, and a dense protective layer was formed by ZnO to improve chemical and thermal stability. Moreover, silicon dioxide was deposited on the surface of the zinc oxide coating using the microemulsion process to strengthen the powder's acid resistance. The double shells structure greatly promoted thermal stability and acid resistance of γ‐Ce2S3 powders. The results showed that rare earth sulfide powders with double shells have good stability for coloring applications. The uncoated γ‐Ce2S3 is easy to decompose and release toxic gas H2S in a humid or acidic environment, and its air thermal stability is limited to 350°C. In this work, we have used heterogeneous precipitation method to coat the surface of γ‐Ce2S3 powder with ZnO nano‐layer, and then used microemulsion method to coat the surface of γ‐Ce2S3@ZnO with SiO2, and successfully prepared γ‐Ce2S3@ZnO@SiO2 composite coating powder. On the premise of not affecting the color rendering performance as much as possible, the thermal stability of γ‐Ce2S3 powder is improved from 350 to 514°C, the time stability is improved from less than 40 days to more than 360 days, and the acid corrosion stability and safety performance are significantly improved.