Significant enhancement of flux pinning in MgB2 superconductor through nano-Si addition

TL;DR

This study demonstrates that adding nano-sized silicon particles to MgB2 significantly enhances flux pinning and critical current density, especially in high magnetic fields, compared to coarse Si or undoped samples.

Contribution

It introduces a novel approach of using nano-Si addition to improve flux pinning in MgB2 superconductors, showing substantial performance gains.

Findings

Nano-Si addition increases critical current density in high fields.

Nano-Si forms Mg2Si and inclusions that enhance flux pinning.

Coarse Si addition does not improve flux pinning as effectively.

Abstract

Polycrystalline MgB2 samples with 10 wt % silicon powder addition were prepared by an in-situ reaction process. Two different Si powders, one with coarse (44 mm) and the other with nano-size (<100 nm) particles were used for making samples. The phases, microstructures, and flux pinning were characterized by XRD, TEM, and magnetic measurements. It was observed that the samples doped with nano-sized Si powder showed a significantly improved field dependence of the critical current over a wide temperature range compared with both undoped samples and samples with coarse Si added. Jc is as high as 3000 A/cm2 in 8 T at 5 K, one order of magnitude higher than for the undoped MgB2. X-ray diffraction results indicated that Si had reacted with Mg to form Mg2Si. Nano-particle inclusions and substitution, both observed by transmission electron microscopy, are proposed to be responsible for the enhancement of flux pinning in high fields. However, the samples made with the coarse Si powders had a poorer pinning than the undoped MgB2.