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 (Ce6Si4S17 determined the crystal structures of Ce2SiS5, Ce4Si3S12, and Ce6Si4S17, 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 Ce3+ ion environments and calculating their electronic band structures. Ce6Si4S17 is distinguished from Ce2SiS5 and Ce4Si3S12 in terms of the Ce3+ structural environment and the Ce3+ 4f --> 5d(0) transition gap. This gap is wider for Ce6Si4S12 than for Ce2SiS5 and Ce4Si3S12 (i.e., 2.51 vs. similar to2.36 eV), and Ce6Si4S17 exhibits room-temperature luminescence whereas Ce2SiS5 and Ce4Si3S12 do not. Ce4Si3S12 and Ce6Si4S17 Possess chromatic properties similar to those found for industrial pigments such as PbCrO4, BiVO4, and CdS, and show thermal and chemical stabilities.