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Synthesis, crystal structure, and chemical stability of the superconductor FeSe 1 − x

2009; American Physical Society; Volume: 80; Issue: 2 Linguagem: Inglês

10.1103/physrevb.80.024517

1550-235X

E. Pomjakushina, K. Conder, Vladimir Pomjakushin, M. Bendele, R. Khasanov,

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We report on a comparative study of the crystal structure and the magnetic properties of ${\text{FeSe}}_{1\ensuremath{-}x}$ $(x=0.0--0.15)$ superconducting samples by neutron powder-diffraction and magnetization measurements. The samples were synthesized by two different methods: a ``low-temperature'' one using powders as a starting material at $T\ensuremath{\simeq}700\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$ and a ``high-temperature'' method using solid pieces of Fe and Se at $T\ensuremath{\simeq}1075\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$. The effect of a starting (nominal) stoichiometry on the phase purity of the obtained samples, the superconducting transition temperature ${T}_{\text{c}}$, as well as the chemical stability of ${\text{FeSe}}_{1\ensuremath{-}x}$ at ambient conditions were investigated. It was found that in the Fe-Se system, a stable phase exhibiting superconductivity at ${T}_{\text{c}}\ensuremath{\simeq}8\text{ }\text{K}$ exists in a narrow range of selenium concentration $({\text{FeSe}}_{0.974\ifmmode\pm\else\textpm\fi{}0.005})$.