Defect structures in MgB2 wires introduced by hot isostatic pressing

TL;DR

This study investigates the microstructural defect formations in MgB2 wires produced by hot isostatic pressing, revealing defect types that enhance flux pinning and improve high-temperature, high-field current performance.

Contribution

It provides detailed microstructural analysis of defect structures in MgB2 wires and links these defects to improved superconducting properties, a novel insight for wire fabrication.

Findings

Presence of crystalline defects forming sub-grains

Defects act as flux pinning centers

Enhanced critical current densities at high temperatures and fields

Abstract

The microstructures of MgB2 wires prepared by the powder-in-tube technique and subsequent hot isostatic pressing were investigated using transmission electron microscopy. Large amount of crystalline defects including small angle twisting, tilting, and bending boundaries, in which high densities of dislocations reside, were found forming sub-grains within MgB2 grains. It is believed that these defects resulted from particle deformation during the hot isostatic pressing process and are effective flux pinning centers that contribute to the high critical current densities of the wires at high temperatures and at high fields.