Effect of the indium addition on the superconducting property and the impurity phase in polycrystalline SmFeAsO1-xFx

TL;DR

This study demonstrates that adding indium to polycrystalline SmFeAsO1-xFx enhances its magnetic critical current density by reducing amorphous impurity phases and improving grain connectivity, leading to better superconducting performance.

Contribution

It is the first to show that indium addition improves superconducting properties by modifying microstructure in SmFeAsO1-xFx.

Findings

Magnetic Jc reaches ~25 kA/cm2 at 4.2 K with indium addition.

Indium reduces amorphous FeAs impurity phases.

Grain connectivity is improved, enhancing superconductivity.

Abstract

We report enhancement in the magnetic critical current density of indium added polycrystalline SmFeAsO1-xFx. The value of magnetic Jc is around 25 kA/cm2 at 4.2 K under self-magnetic field. Polycrystalline SmFeAsO1-xFx is mainly composed of the superconducting grains and a little of amorphous FeAs compounds. These areas randomly co-exist and amorphous areas are located between superconducting grains. Therefore, the superconducting current is prevented by the amorphous areas. In this study, it is found that indium addition to polycrystalline SmFeAsO1-xFx removes these amorphous areas and induces the bringing together the superconducting grains. It means the total contact surfaces of grains are increased. We suggest that the enhancement of the magnetic critical current density is a direct effect of the indium addition.