Calorimetric evidence for enhancement of homogeneity in high performance Sr1-xKxFe2As2 superconductors

TL;DR

This study demonstrates that hot-pressing improves the homogeneity and superconducting properties of Sr1-xKxFe2As2 tapes by reducing anomalies and enhancing critical current density, compared to rolled tapes.

Contribution

It provides experimental evidence that high-pressure sintering enhances dopant distribution and superconducting homogeneity in Sr1-xKxFe2As2 tapes.

Findings

Hot-pressed tapes show no Schottky anomaly in specific heat.

Hot-pressed tapes have higher superconducting fraction.

Homogeneity of superconducting transition improves with hot-pressing.

Abstract

We comparatively studied the critical current density, magnetization and specific heat of the rolled and the hot-pressed Sr1-xKxFe2As2 tapes. The Schottky anomaly that is obvious in the specific heat of the rolled tape disappears in the hot-pressed tape. Moreover, the hot-pressed tape has a higher fraction of superconductivity and a narrower distribution of superconducting transition temperature than the rolled tape. Combined with the magnetization data, we conclude that sintering under high pressure provides a better environment for complete chemical reaction and more homogenous dopant distribution, which is beneficial to the global current of a superconductor.