Superconductivity at 40 K in Lithiation-Processed [(Fe,Al)(OH)2][FeSe]1.2 with a Layered Structure

• Published in: Inorganic chemistry Vol. 60; no. 6; pp. 3902 - 3908
• Main Authors: Hu, Guobing, Shi, Mengzhu, Wang, Wenxiang, Zhu, Changsheng, Sun, Zeliang, Cui, Jianhua, Zhuo, Weizhuang, Yu, Fanghang, Luo, Xigang, Chen, Xianhui
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 15.03.2021
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.0c03686

Exploration of new superconductors has always been one of the research directions in condensed matter physics. We report here a new layered heterostructure of [(Fe,Al)­(OH)2]­[FeSe]1.2, which is synthesized by the hydrothermal ion-exchange technique. The structure is suggested by a combination of X-ray powder diffraction and the electron diffraction (ED). [(Fe,Al)­(OH)2]­[FeSe]1.2 is composed of the alternating stacking of a tetragonal FeSe layer and a hexagonal (Fe,Al)­(OH)2 layer. In [(Fe,Al)­(OH)2]­[FeSe]1.2, there exists a mismatch between the FeSe sublayer and the (Fe,Al)­(OH)2 sublayer, and the lattice of the layered heterostructure is quasi-commensurate. The as-synthesized [(Fe,Al)­(OH)2]­[FeSe]1.2 is nonsuperconducting due to the Fe vacancies in the FeSe layer. The superconductivity with a T c of 40 K can be achieved after a lithiation process, which is due to the elimination of the Fe vacancies in the FeSe layer. The T c is nearly the same as that of (Li,Fe)­OHFeSe although the structure of [(Fe,Al)­(OH)2]­[FeSe]1.2 is quite different from that of (Li,Fe)­OHFeSe. The new layered heterostructure of [(Fe,Al)­(OH)2]­[FeSe]1.2 contains an iron selenium tetragonal lattice interleaved with a hexagonal metal hydroxide lattice. These results indicate that the superconductivity is very robust for FeSe-based superconductors. It opens a path for exploring superconductivity in iron-base superconductors.