Topotactic fluorination of intermetallics as an efficient route towards quantum materials

Insertion of light elements in intermetallics has been explored to synthesize functional materials. Here the authors report topotactic intercalation of fluorine atoms into intermetallics using a perfluorocarbon reactant with covalent C-F bonds to obtain quantum materials. Intermetallics represent an important family of compounds, in which insertion of light elements (H, B, C, N) has been widely explored for decades to synthesize novel phases and promote functional materials such as permanent magnets or magnetocalorics. Fluorine insertion, however, has remained elusive so far since the strong reactivity of this atypical element, the most electronegative one, tends to produce the chemical decomposition of these systems. Here, we introduce a topochemical method to intercalate fluorine atoms into intermetallics, using perfluorocarbon reactant with covalent C-F bonds. We demonstrate the potential of this approach with the synthesis of non-stoichiometric mixed anion (Si-F) LaFeSiFx single-crystals, which are further shown to host FeSi-based superconductivity. Fluorine topochemistry on intermetallics is thus proven to be an effective route to provide functional materials where the coexistence of ionic and metallo-covalent blocks, and their interactions through inductive effects, is at the root of their functional properties.

Automated summary

This article introduces a topochemical method for intercalating fluorine atoms into intermetallics and demonstrates its potential by synthesizing non-stoichiometric mixed anion LaFeSiFx single crystals, which exhibit FeSi-based superconductivity. The study shows that fluorine topochemistry on intermetallics is an effective route for providing functional materials.