Observation of superconductivity at 30~46 K in A(x)Fe₂Se₂(A = Li, Na, Ba, Sr, Ca, Yb, and Eu).
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.
Research & Development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
T P
TP
Ying
X L
XL
Chen
G
G
Wang
S F
SF
Jin
T T
TT
Zhou
X F
XF
Lai
H
H
Zhang
W Y
WY
Wang
D001464:Barium / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D004553:Electric Conductivity; D006358:Hot Temperature; D058085:Iron Compounds / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry; D060526:Magnetic Fields; D012643:Selenium / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry; D014961:X-Ray Diffraction; D015018:Ytterbium / Q000737:chemistry
D058085:Iron Compounds; D001464:Barium; D008094:Lithium; D012964:Sodium; D012643:Selenium; D015018:Ytterbium; D002118:Calcium