Electron microscopic study of the system mPbS‐nBi₂S₃

A systematic search is performed for intermediate phases in the whole PbS‐Bi₂S₃ range. At the Pb‐rich side of the phase diagram, no new phases are detected apart from the known phases heyrovskite and lillianite. At the Bi‐rich side of the phase diagram between galenobismutite and bismuthinite, some new V‐phases are discovered, the diffraction pattern of which varies quasi continuously with composition in a similar fashion asobserved previously in N_3±x, Te₂, and Cu_3−x, Te₂. It is possible to describe the structure of all the phases by a unified model based on periodic twinning of the galena matrix. A high temperature study shows that the Pb rich phases are likely to be formed by the propagation of twinned hairpins in the galena matrix which allows to explain why no other phases are found.