Synthesis and stability of single-phase chalcopyrite - a potential reference material for key investigations in chemistry and metallurgical engineering

Single-phase chalcopyrite (CuFeS2) is a key reference material in the development of new metallurgical processes to ensure a reliable copper supply. Here, we report on the successful synthesis of single-phase chalcopyrite and its phase behaviour. We further rationalise different opinions previously expressed in the literature. Chalcopyrite synthesis has been studied at 450 degrees C with varying sulfur contents and analysed using X-ray powder diffraction (XRPD) and Fe-57-Mossbauer spectroscopy. With stoichiometric amounts (Cu : Fe : S = 25 : 25 : 50) the main chalcopyrite phase is contaminated with pyrite (FeS2) and bornite (Cu5FeS4). Single-phase chalcopyrite was only found in samples containing around 49.7 at% sulfur in the reactant mixture. Mossbauer spectroscopy confirmed that chalcopyrite contains trivalent iron. Temperature dependent XRPD measurements detected an order-disorder phase transition starting at 485 degrees C. At temperatures above 535 degrees C, samples only contained intermediate solid solutions. These adopt the sphalerite structure with the lattice constant slightly varying with Cu : Fe ratio.

Automated summary

The study focuses on the successful synthesis of single-phase chalcopyrite, its phase behavior, and rationalization of different opinions in the literature. Results show that single-phase chalcopyrite requires a specific sulfur content, with an order-disorder phase transition occurring at high temperatures. Additionally, the presence of other sulfur-containing substances was observed in the experiments.