Characterization of FeSe x Superconductor Prepared by Different Thermal Routes by Instrumented Indentation

Abstract

The present work reports on the characterization of granular FeSex superconductor. Two groups of polycrystalline samples were produced by different thermal routes trough a conventional solid-state reaction. The pellets were characterized by scanning electron microscopy, X-ray diffraction and electrical-resistivity measurements. Also, the elastic modulus at room temperature was measured by instrumented indentation. From X-ray analysis, we observed the presence of the α-FeSe1−x, β-FeSe1−x and Fe7Se8 phases for one group of samples and only the β-FeSe1−x and Fe7Se8 phases for another group, besides some minority phases. These results agree with resistivity measurements in which it was observed that for the first group of samples, where α-FeSe1−x is present, the superconductor behavior is noticed to have TC∼8 K, while the other group does not show superconductivity. Elastic modulus for both samples indicated values around 42 GPa at the deepest tip penetration depth. The E/H ratio for these samples is in between those of metals and brittle materials.