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Polycrystalline samples of FeSe 0.5 Te 0.5 were synthesized using a conventional solid-state reaction method. The onset of bulk superconductivity transition was confirmed by SQUID magnetometry at 12.5 K. 57 Fe Mössbauer spectra in transmission geometry were recorded at temperatures between 6.0 and 320 K. Both the isomer shift and the total absorption started to drop about T c , indicating a softening of the lattice. The drop is estimated to correspond to at least 60 K from the original Debye temperature θ D ≈ 460 K. Seebeck measurements indicate that the samples are n-type conductors at low temperatures with a cross-over to p-type conductivity around 135 K. The zero Seebeck coefficient is seen below 10.6 K.

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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