Topotactic synthesis of a new BiS2-based superconductor Bi2(O,F)S2

TL;DR

This paper reports the discovery and synthesis of a new BiS2-based superconductor, Bi2(O,F)S2, achieved through topotactic fluorination, which enhances its superconducting transition temperature to 5.1 K.

Contribution

First topotactic synthesis of an electron-doped BiS2 superconductor via reductive fluorination using XeF2.

Findings

Superconductor Bi2(O,F)S2 was successfully synthesized.

Tc increased to 5.1 K with F doping.

Structural changes correlated with F content.

Abstract

A new BiS2-based superconductor Bi2(O,F)S2 was discovered. This is a layered compound consisting of alternate stacking structure of rock-salt-type BiS2 superconducting layer and fluorite-type Bi(O,F) blocking layer. Bi2(O,F)S2 was obtained as the main phase by topotactic fluorination of undoped Bi2OS2 using XeF2, which is the first topotactic synthesis of an electron-doped superconductor via reductive fluorination. With increasing F-content, a- and c-axis length increased and decreased, respectively, and Tc increased up to 5.1 K.