Mechanical properties of highly oriented FeSe0.5Te0.5 superconductor

Abstract

We have synthesized highly oriented samples of the superconducting compound FeSe0.5Te0.5 and investigated its mechanical properties. These samples were characterized by scanning electron microscopy (SEM) with energy-dispersive analysis, x-ray diffraction, and electrical resistivity. The measured critical temperature is TC~ 14.5 K. Hardness and elastic modulus on the ab- and a(b)c-plane were obtained by instrumented indentation. The samples’ morphology consists of plate-like crystals with a lamellar structure. Two phases were observed with a typically eutectic microstructure composed by white and gray lamellas when observed with SEM using backscattered electrons. The white phase is richer in Te and poorer in Se than the gray phase. No significant differences in hardness and elastic modulus were observed between ab- and a(b)c-planes. Hardness profiles indicated values in the range 0.6–0.8 GPa at deep tip penetration depths, while the elastic modulus showed values in between 20–25 GPa. Cracking was occasionally observed in the ab-plane and at low loads.

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“…As previously summarized in section 1, the above elastic modulus values are in the same order than those observed in iron-based superconductors (20-55 GPa [10,11]), and lower than values reported for cuprates (107-165 GPa [12,13]). Likewise, the measured hardness (1.6 GPa) is similar to values found for iron-based compounds (0.6-3.4 GPa [10,11]) and lower than those reported for cuprates (7.3-8 GPa [12,13]).…”

“…As previously summarized in section 1, the above elastic modulus values are in the same order than those observed in iron-based superconductors (20-55 GPa [10,11]), and lower than values reported for cuprates (107-165 GPa [12,13]). Likewise, the measured hardness (1.6 GPa) is similar to values found for iron-based compounds (0.6-3.4 GPa [10,11]) and lower than those reported for cuprates (7.3-8 GPa [12,13]). From a tribological point of view, neither hardness nor elastic modulus alone can predict adequately the material's behavior, since wear mechanisms involve both plastic and elastic strains, in synergy [24].…”

“…For instance, iron-based superconductors as the highly oriented FeSe 0.5 Te 0.5 presented hardness and elastic modulus with values in the range 0.6-0.8 GPa and 20-25 GPa, respectively, for both ab-and a(b)c-planes. Cracking was eventually observed in the ab-plane and under low normal loads [10]. Anisotropic hardness values were found in BaFe 2 As 2 single crystals, namely 3.4 GPa for the ab-and 1 GPa in the a(b)c-plane, whereas elastic modulus was around of 55 GPa in both crystallographic planes [11].…”