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Observation of superconductivity at 30∼46K in AxFe2Se2(A = Li, Na, Ba, Sr, Ca, Yb and Eu)

2012; Nature Portfolio; Volume: 2; Issue: 1 Linguagem: Inglês

10.1038/srep00426

2045-2322

Tianping Ying, X. L. Chen, Gang Wang, Shifeng Jin, Tingting Zhou, Xiaofang Lai, H. Zhang, W. Y. Wang,

Superconductivity in MgB2 and Alloys

New iron selenide superconductors by intercalating smaller-sized alkali metals (Li, Na) and alkaline earths using high-temperature routes have been pursued ever since the discovery of superconductivity at about 30 K in KFe₂Se₂, but all have failed so far. Here we demonstrate that a series of superconductors with enhanced T(c) = 30∼46 K can be obtained by intercalating metals, Li, Na, Ba, Sr, Ca, Yb, and Eu in between FeSe layers by the ammonothermal method at room temperature. Analysis on their powder X-ray diffraction patterns reveals that all the main phases can be indexed based on body-centered tetragonal lattices with a∼3.755-3.831 Å while c∼15.99-20.54 Å. Resistivities show the corresponding sharp transitions at 45 K and 39 K for NaFe₂Se₂ and Ba₀.₈Fe₂Se₂, respectively, confirming their bulk superconductivity. These findings provide a new starting point for studying the properties of these superconductors and an effective synthetic route for the exploration of new superconductors as well.