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Abstract:
The 11-type Fe-chalcogenides belong to the family of Fe-based superconductors. In these compounds, the interstitial Fe is known to strongly influence the magnetic and superconducting properties. Here, we present the chemical homogeneity range of ternary compounds Fe1 + y Te1-x Se (x) based on powder x-ray diffraction, energy dispersive x-ray analysis, and magnetization measurements. Our investigations show that the maximum amount of excess Fe in homogeneous Fe1 + y Te1-x Se (x) decreases with increase in Se substitution for Te. Using our synthesis procedure, single-phase Fe1 + y Te1-x Se (x) , with 0.5 ae<currency> x < 1 could not be formed for any amount of excess Fe. Further, the superconducting volume fraction in the material is found to be strongly suppressed by excess Fe.
