Cometal addition effect on superconducting properties and granular behaviours of polycrystalline FeSe0.5Te0.5

TL;DR

This study investigates how adding small amounts of Pb and Sn to polycrystalline FeSe0.5Te0.5 enhances its superconducting properties by improving phase uniformity and flux pinning, with optimal results at 2wt% additions.

Contribution

It demonstrates that minor cometal additions improve superconducting transition temperature, critical current density, and flux pinning in FeSe0.5Te0.5, which is a novel approach for optimizing these materials.

Findings

Small Pb and Sn additions increase Tconset by 1 K.

2wt% cometal additions yield the best Jc and Fp performance.

Excessive additions reduce superconducting quality due to impurity phases.

Abstract

The enhanced performance of superconducting FeSe0.5Te0.5 materials with added microsized Pb and Sn particles is presented. A series of Pb and Sn added FeSe0.5Te0.5 (FeSe0.5Te0.5 + xPb + ySn; x = y = 0-0.1) bulks are fabricated by solid-state reaction method and characterized through various measurements. A very small amount of Sn and Pb additions enhance the transition temperature (Tconset) of pure FeSe0.5Te0.5 by 1 K, sharpening the superconducting transition and improving the metallic nature in the normal state, whereas larger metal additions reduce Tconset by broadening the superconducting transition. Microstructural analysis and transport studies suggest that at x=y>0.02, Pb and Sn additions enhance the impurity phases, reduce the coupling between grains, and suppress the superconducting percolation, leading to a broad transition. FeSe0.5Te0.5 samples with 2wt% of cometal additions show the best performance with their critical current density, Jc, and the pinning force, Fp, which might be attributable to providing effective flux pinning centres. Our study shows that the inclusion of a relatively small amount of Pb and Sn works effectively for the enhancement of superconducting properties with an improvement of intergrain connections as well as better phase uniformity.