A novel iron-based superconductor synthesized by the ion exchange technique

Abstract

The superconductivity of the FeSe-based superconductor is extremely sensitive to Fe vacancies in the FeSe plane. In order to reduce the formation of Fe vacancies in the FeSe plane, various low-temperature methods are developed. However, it is still complex and time consuming to control the Fe vacancies concentration. Here, a hybrid iron-based superconductor, Li0.21Se0.05(EG)0.26FeSe (EG: Ethylene glycol, C2H6O2), is synthesized by a solvothermal ion-exchange technique using a nearly vacancy-free precursor of (TBA)0.3FeSe as the matrix. Bulk superconductivity with transition temperature (Tc) of 30 K is confirmed by the characterization with the magnetic susceptibility and resistivity measurements. Compared with the pristine FeSe single crystal, XPS results show a decrease of the Fe valence, indicating that electron doping to FeSe plane accounts for the increase of the Tc. Our result suggests that (TBA)0.3FeSe, a nearly vacancy-free precursor with a large distance between the adjacent FeSe planes, is a good template candidate for the synthesis of other hybrid iron-based superconductors using the ion exchange technique.

Advances in Chalcogenide Crystal Growth: Flux and Solution Syntheses, and Approaches for Postsynthetic Modifications

“…In this case, postsynthetic modification allowed single-crystal property measurements and unarguably determined that the FeS mackinawite phase is a 3D superconductor with highly anisotropic properties. More than ten intercalated-FeSe phases are known to be superconductors; ,− however, only a couple of them were obtained as single crystals, and structural characterization was performed via SC-XRD. For instance, the [(Fe,Al)­(OH) 2 ]­[FeSe] 1.2 superconductor with T c ≈ 40 K was obtained from postsynthetic modification of K 0.8 Fe 2 Se 2 single crystals; however, the resulting material did not remain a single crystal.…”