溶融硫黄を用いるPbTiS3 およびBa xTiSyの合成におけるハライド添加の効果

On the synthesis of mixed metal sulfides in sulfur melt, the yield is greatly affected by the addition of halides. The respective effects of PbX2 on PbTiS3 and BaX2 (X = F, Cl and I) on BaxTiSy yield were studied for the reaction in evacuated sealed ampoules at 350~ °C for 7 days. The starting materials were 0.9 Pb + 0.1 PbX2 + TiS2 + 50S and 0.9 BaS + 0.1 BaX2 + TiS2 + 50S. In the former reactions, PbCl2 caused a large increase in the yield at lower temperatures, viz. 350 °C. On the other hand, BaI2 was most effective giving 96 % yield of BaxTiSy at 450 °C. The yield enhancement at lower temperatures seems to be associated with the higher concentration of metal ions (Pb2+) 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.