Superconductivity in WO2.6F0.4 synthesized by reaction of WO3 with Teflon

TL;DR

This study reports the synthesis of WO2.6F0.4 oxyfluoride via fluorination of WO3 using Teflon, revealing a transition from insulator to superconductor at low temperatures with potential for discovering new oxyfluoride superconductors.

Contribution

It introduces a simple fluorination method to synthesize oxyfluoride superconductors and characterizes their structural and electronic properties.

Findings

Fluorine doping induces metallicity in WO3.

Superconductivity observed at Tc = 0.4 K in specific fluorine content range.

Crystal symmetry changes with fluorine content.

Abstract

WO3-xFx (x < 0.45) perovskite-like oxyfluorides were prepared by a chemically reducing fluorination route using the polymer polytetrafluoroethylene (Teflon). The symmetry of the crystal structures of WO3-xFx changes from monoclinic to tetragonal to cubic as the fluorine content increases. Fluorine doping changes insulating WO3 to a metallic conductor, and superconductivity (Tc = 0.4 K) was discovered in the samples with fluorine contents of 0.41 < x < 0.45. This easy fluorination method may be applicable to other systems and presents an opportunity for finding new oxyfluoride superconductors.