Effect of Pb addition on microstructure, transport properties and the critical current density in a polycrystalline FeSe0.5Te0.5

TL;DR

This study examines how adding lead (Pb) to FeSe0.5Te0.5 superconductors affects their structure, electrical, and magnetic properties, revealing that small Pb additions can enhance critical current density despite reducing transition temperatures.

Contribution

It provides new insights into how Pb doping influences microstructure and superconducting performance, especially the increase in critical current density at small doping levels.

Findings

Pb enhances metallic behavior but lowers Tc with increased doping.

Small Pb addition (x=0.05) increases critical current density.

Higher Pb levels weaken grain coupling and suppress superconductivity.

Abstract

We have investigated the effects of lead (Pb) additions (x) up to 40 wt.% (x = 0-0.4) on the structure, electrical properties, and magnetic properties of FeSe0.5Te0.5 superconductor. The samples were prepared by the solid-state reaction method and characterized by various techniques. The parent compound (x = 0) showed the onset temperature Tc onset of 15 K, and zero-resistance temperature, Tc offset of 12 K. The addition of Pb enhances the metallic characteristics of FeSe0.5Te0.5, but both Tc onset and Tc offset are decreased to the lower temperature with the broadened transition width. The Tc onset is nearly the same (10.3 K) at higher additions, such as x = 0.3 and 0.4, but zero resistivity is not observed up to 7 K. Microstructural analysis and transport studies suggest that for x > 0.05, Pb additions weakened the coupling between grains and suppressed the superconducting percolation, leading to a broad transition. More importantly, the inclusion of a relatively small amount of Pb (x = 0.05) increased the critical current density, Jc, in the entire magnetic field, which might be attributable to better phase uniformity as well as good grain connectivity.