Enhancement of the in-field Jc of MgB2 via SiCl4 doping

TL;DR

This study demonstrates that doping MgB2 with liquid SiCl4 significantly improves its critical current density and magnetic field performance, offering a C-free doping method that enhances flux pinning and superconducting properties.

Contribution

Introduction of liquid SiCl4 as a C-free dopant that enhances MgB2's superconducting properties and the development of a new parameter RHH to evaluate flux pinning improvements.

Findings

SiCl4 doping increases Jc and Hirr with minimal Tc reduction.

Si does not incorporate into the lattice but reduces the a-axis parameter.

SiCl4 treated MgB2 outperforms other doped variants above 20 K.

Abstract

In this work, we present the following important results: 1) We introduce a new Si source, liquid SiCl4, which is free of C, to significantly enhance the irreversibility field (Hirr), the upper critical field (Hc2), and the critical current density (Jc), with little reduction in the critical temperature (Tc). 2) Although Si can not incorporate into the crystal lattice, we found a reduction in the a-axis lattice parameter, to the same extent as for carbon doping. 3) The SiCl4 treated MgB2 shows much higher Jc with superior field dependence above 20 K than undoepd MgB2 and MgB2 doped with various carbon sources. 3) We provide an alternative interpretation for the reduction of the a lattice parameter in C- and non-C doped MgB2. 4). We introduce a new parameter, RHH (Hc2/Hirr), which can clearly reflect the degree of flux pinning enhancement, providing us with guidance for further enhancing Jc. 5) We have found that spatial variation in the charge carrier mean free path is responsible for the flux pinning mechanism in the SiCl4 treated MgB2 with large in-field Jc.