BSE micrographs of Co-Se-Sn samples long-time annealed at 400 °C, 600 °C and 1000 °C

For updated version go to https://doi.org/10.5281/zenodo.17354287The uploaded dataset contains back-scattered electron (BSE) micrographs for every sample listed in Tables 2–4. The samples were annealed for long-time periods at 400 °C, 600 °C and 1000 °C, then metallographically ground, polished and examined with a JEOL JSM-6460 scanning electron microscope. BSE imaging was chosen to maximise the material contrast. Representative samples from individual phase fields are presented in this paper. The complete micrograph set provided here forms the experimental basis for the isothermal sections of the Co-Se-Sn ternary phase diagrams constructed at the corresponding temperatures.