Syntheses, Structures, and Optical Properties of Yellow Ce2SiS5, Ce6Si4S17, and Ce4Si3S12 Materials

The Ce−S−Si system has been explored in search of new, yellow nontoxic pigments. We prepared a new Ce−S−Si phase (Ce 6 Si 4 S 17 ), determined the crystal structures of Ce 2 SiS 5, Ce 4 Si 3 S 12, and Ce 6 Si 4 S 17, and measured the chromatic properties of these Ce−S−Si phases. The differences in the yellow hue of these compounds were probed by analyzing their Ce 3+ ion environments and calculating their electronic band structures. Ce 6 Si 4 S 17 is distinguished from Ce 2 SiS 5 and Ce 4 Si 3 S 12 in terms of the Ce 3+ structural environment and the Ce 3+ 4f 1 →5d 0 transition gap. This gap is wider for Ce 6 Si 4 S 17 than for Ce 2 SiS 5 and Ce 4 Si 3 S 12 (i.e., 2.51 vs. ∼2.36 eV), and Ce 6 Si 4 S 17 exhibits room-temperature luminescence whereas Ce 2 SiS 5 and Ce 4 Si 3 S 12 do not. Ce 4 Si 3 S 12 and Ce 6 Si 4 S 17 possess chromatic properties similar to those found for industrial pigments such as PbCrO 4, BiVO 4, and CdS, and show thermal and chemical stabilities.