Superconductivity in Vacuum Annealed Bi₆O₈S₅

Abstract

Bi6O8S5, the parent compound of the Bi4O4S3 superconductor, is found to display typical insulating behavior via transport measurement. Here we report that the samples annealed at 200 and 250 °C in vacuum exhibit superconductivity below around 4.2 K. Samples annealed at neighboring temperatures also display superconducting transitions in the ρ∼ T curves, but no diamagnetic signals are observed in the \(M\sim T\) curves. Comparison of the XRD patterns for the samples before and after annealing suggests visible shrinkage of the lattice parameters in the superconducting samples. The phenomenon coincides with the case of the annealing induced superconductivity for FeTe0.8S0.2.