Abstract
Rare earth copper sulfides, LnCuS2 (Ln=Ce, Pr, Nd, Sm, Gd and Tb), powders were synthesized by the following procedure: (1) Ln-Cu complex oxide was synthesized using the polymerized complex method, and (2) LnCuO2 was sulfurized by the CS2 gas. CS2 gas sulfurization combined with a polymerized complex method can reduce a reaction temperature and a duration time. TG-DTA and XRD results indicated that Ln′-Cu polymerized complex (Ln=Pr, Nd, Sm and Gd) was decomposed into Ln′2O3 (via Ln′2OCO3) and Cu/CuO. Ln′2O3 reacted with CuO to form Ln′2CuO4 complex oxide. In the case of Ce and Tb (Ln″), a Ln″-Cu polymerized complex was decomposed into Ln″O2 and Cu/CuO. Ln″2CuO4 phase was not observed in these cases. In sulfurization reaction, XRD indicates that Ln′CuS2 was formed via a formation of Ln′OCuS. On the other hand, Ln″CuS2 is considered to be formed via a solid state reaction between Ln″2S3 and Cu2S. The contents of oxygen and carbon impurities in the products depend on the sulfurization reaction conditions. For example, the PrCuS2 powder was obtained with low impurity contents of 0.07 mass% C and 0.073 mass% O by sulfurization at 1223 K.
