Effect of Halide Addition on the Syntheses of PbTiS 3 and Ba x TiS y in Sulfur Melt

Abstract

On the synthesis of mixed metal sulfides in sulfur melt, the yield is greatly affected by the addition of halides. The respective effects of PbX 2 on PbTiS 3 and BaX 2 (X = F, Cl and I) on Ba x TiS y yield were studied for the reaction in evacuated sealed ampoules at 350 450 ° C for 7 days. The starting materials were 0.9 Pb + 0.1 PbX 2 + TiS 2 + 50S and 0.9 BaS + 0.1 BaX 2 + TiS 2 + 50S. In the former reactions, PbCl 2 caused a large increase in the yield at lower temperatures, viz. 350 ° C. On the other hand, BaI 2 was most effective giving 96 % yield of Ba x TiS y at 450 ° C. The yield enhancement at lower temperatures seems to be associated with the higher concentration of metal ions (Pb 2+) or the higher solubility of PbS in sulfur melt. The main effect at higher temperatures seems to be that to suppress the sulfur vapor pressure, which reduces the formation of high volatility sulfide by-products.