Phase relations and structure–properties correlations in Fe(S,Se,Te)

• Published in: Physica. C, Superconductivity Vol. 539; pp. 19 - 24
• Main Authors: Abouhaswa, A.S., Selezneva, N.V., Merentsov, A.I., Neznakhin, D.S., Baranov, N.V.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-08-2017; Elsevier BV
• Subjects: Chemical composition; Diffraction; Hexagonal phase; Interlayer distance; Interlayers; Iron based superconductors; Phase relations; Physical properties; Scanning electron microscopy; Selenium; Sulfur; Sulfur content; Superconductivity; Superconductors; Tellurium; Ternary mixture; Iron based superconductors; Chemical composition; Phase relations; Interlayer distance; Ternary mixture
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/j.physc.2017.06.004

•Three series of polycrystalline samples with compositions Fe1.02TeySe1−y−xSx have been synthesized.•The S for Se substitution in Fe1.02TeySe1−y−xSx results in the growth of the average interlayer distance in the superconducting tetragonal phase.•Replacement of selenium by sulfur in Fe1.02TeySe1−y−xSx also results in the growth of the volume fraction of the hexagonal phase.•We found that the Tconset values decrease near linearly with increasing lattice parameter c of tetragonal phase.
Three series of polycrystalline samples with nominal compositions Fe1.02TeySe1−y−xSx (y = 0.3, 0.4, 0.6 and 0≤x≤0.7) have been synthesized and studied by means of the X-ray diffraction, scanning electron microscopy, electrical resistivity and magnetization measurements. Together with the tetragonal superconducting phase, all the samples have been found to contain a hexagonal phase of the NiAs-type; and the increase in sulfur content leads to a redistribution of various chalcogens between phases due to the difference in solubility limits and variations of the chemical compositions and volume fractions of these phases. The sulfur for selenium substitution in Fe1.02TeySe1−y−xSx results in a growth in the average interlayer distance in the superconducting tetragonal phase because of its enrichment by tellurium and depletion in sulfur; while the hexagonal phase becomes enriched by sulfur and depleted in tellurium with increasing sulfur content in the samples. It has been shown that in the Fe(Te,Se,S) materials with ternary mixture of chalcogens, the variation of the critical superconducting temperature correlates with the change in the average interlayer distance in the tetragonal structure as in other FeSe-based materials.