Migration of ferrous ions (Fe2+) during the synthesis of (Li,Fe)OHFeSe by ion exchange technology

• Published in: New Journal of Physics
• Main Authors: G B Hu, M Z Shi, Z G Zhang, X H Chu, W W Liu, J F Guo, M Gao, T Y Duan, X G Luo
• Format: Article
• Language: English
• Published: IOP Publishing 2025-01-01
• Subjects: superconductivity; FeSe-based superconductor; ion exchange; (Li,Fe)OHFeSe; Fe vacancies; migration of ferrous ions
• Online Access: https://doi.org/10.1088/1367-2630/add7ff

Iron-based superconductors (FeSCs), particularly the air-stable (Li,Fe)OHFeSe, have drawn considerable attention due to their complex crystalline structures and intriguing superconducting properties. This study focuses on the synthesis of (Li,Fe)OHFeSe, using hydrothermal ion exchange technology with a nearly vacancy-free (PY) _x FeSe precursor. We successfully synthesized samples in both iron-poor and iron-rich reaction systems, with the iron-rich samples exhibiting superconductivity at a transition temperature ( T _c ) of 40 K, while iron-poor samples did not. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) results showed an obvious difference in Se content between the original solutions of iron-poor and iron-rich systems after the hydrothermal reaction. We propose that in iron-rich system, Fe ^2+ ions migration into the (Li,Fe)OH layer from the reaction solution directly maintains the stability of the FeSe layer in the precursor, facilitating superconductivity. Conversely, in iron-poor system, Fe ^2+ ions migrate into the (Li,Fe)OH layer partly from the reaction solution and partly from the FeSe layer, creating Fe vacancies in the FeSe layer, which inhibit the occurrence of superconductivity. Our findings provide valuable insights into the synthesis of intercalated FeSe-based superconducting materials and the realization of superconductivity in FeSe based superconducting materials.