Cometal Addition Effect on Superconducting Properties and Granular Behaviours of Polycrystalline FeSeTe.

The enhanced performance of superconducting FeSeTe materials with added micro-sized Pb and Sn particles is presented. A series of Pb- and Sn-added FeSeTe (FeSeTe + Pb + Sn; = = 0-0.1) bulks are fabricated by the solid-state reaction method and characterized through various measurements. A very small amount of Sn and Pb additions ( = ≤ 0.02) enhance the transition temperature () of pure FeSeTe by ~1 K, sharpening the superconducting transition and improving the metallic nature in the normal state, whereas larger metal additions ( = ≥ 0.03) reduce by broadening the superconducting transition. Microstructural analysis and transport studies suggest that at > 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. FeSeTe samples with 2 wt% of cometal additions show the best performance with their critical current density, , and the pinning force, , 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 ( = ≤ 0.02) works effectively for the enhancement of superconducting properties with an improvement of intergrain connections as well as better phase uniformity.