The effect of nanoscale Fe doping on the superconducting properties of MgB₂

Abstract

Iron is an important sheath material for fabrication of MgB 2 wires. However, the effect of Fe doping on the superconducting properties of MgB 2 remains controversial. In this work, we present results of nanoscale Fe particle doping in to MgB 2 . The Fe doping experiments were performed using both bulk and thin film form. It was found that Fe doping did not affect the lattice parameters of MgB 2 , as evidenced by the lack of change in the XRD peak positions for MgB 2 . Because of the high reactivity of nano-scale Fe particles, Fe doping is largely in the form of FeB at low doping level while Fe 2 B was detected at 10wt% doping by both XRD and TEM. There is no evidence for Fe substitution for Mg. The transition temperature decreased modestly with increasing Fe doping levels. The J c (H) performance was severely depressed at above 3wt% doping level. The detrimental effect of nano-scale Fe doping on both T c and J c (H) is attributable to the grain decoupling as a result of magnetic scattering of Fe-containing dopants at grain boundaries.

Fluxoid jump coupled high critical current density of nano-Co3O4doped MgB2

“…Not only the amount of added Mg turnings but the heating rate also controls the amount of Mg/MgO in the end product. In the present study instead of using Mg/MgO as pinning centers in MgB 2 , we added nano-Co 3 O 4 in the pristine We also compare our present results of nano-Co 3 O 4 doped MgB 2 with various other reports [3][4][5][6][7][8] on different nano-particle doped MgB 2 . We found that in most of the nano-particle doped MgB 2 , the high J c is coupled with low field and low temperature fluxiod jumps.…”

“…By now a number of articles had appeared on the critical current density of nano particle doped MgB 2 for example nano-SiO 2 [3], nano-Fe [4], nano-diamond [5], nano-SiC [6], nanoTiO 2 [7], nano-Al 2 O 3 [8] and others. Not only the doped nano-particles but various routes of synthesis had also resulted in improved critical current density of this compound [9,10].…”

Flux pinning and inhomogeneity in magnetic nanoparticle doped MgB2/Fe wires

“…Although most publications report enhancement of in-field J c and B irr [6,7,8,9] upon doping of MgB 2 with magnetic nanoparticles, the actual situation is not so clear. In particular, there are some observations of detrimental influence of magnetic nanoparticles on J c of MgB 2 [10,11] and also direct, transport J c measurements on MgB 2 wires doped with magnetic nanoparticles are still lacking.…”

Microstructural Features of Magnetic NiCoB Nanoparticles Addition to MgB2 Precursor Powders

“…On contrary, either the sizes of the MgB2 crystallites in the resulting MgB2 sample (formed after the addition of the nanoparticles to Mg and B precursor powders and sintering at various temperatures) are given, [20] or they do not give any information about the sizes of the crystallites. [21,[23][24][25] The same stands for the MgB2 grain sizes determined from electron microscopy observation (mostly from SEM). This work gives an insight in how the addition of the NiCoB nanoparticles affects the sizes of the grains of the constituent phases and elements present in the resulting MgB2 sample (including the information of size and shapes of constituent crystallites in case of MgB2 grains).…”