Original scientific paper

https://doi.org/10.5562/cca2985

Microstructural Features of Magnetic NiCoB Nanoparticles Addition to MgB₂ Precursor Powders

Ivana Lončarek ; Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, HR-10000 Zagreb, Croatia
Anđelka M. Tonejc ; Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, HR-10000 Zagreb, Croatia
Željko Skoko orcid.org/0000-0003-3000-7353 ; Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, HR-10000 Zagreb, Croatia
Nikolina Novosel ; Institute of Physics, Zagreb, Bijenička cesta 46, HR-10000, Croatia
Mislav Mustapić ; Josip Juraj Strossmayer University of Osijek, Department of Physiscs, Trg ljudevita Gaja 6, HR-31000 Osijek, Croatia

Abstract

Magnesium diboride (MgB2) is a superconductor characterized by interesting properties like rather high superconducting transition temperature Tc = 39 K, long coherence length and low anisotropy. In addition, it has a very simple crystal structure and low density. Those properties make the MgB2 an ideal candidate for a wide range of applications.
To improve the electromagnetic properties of MgB2, magnetic nickel-cobalt-boron (NiCoB) nanoparticles (mean grain size 17 ± 3 nm) were added to Mg and B precursor powders and sintered at 650 °C, i.e. the temperature of MgB2 superconductor formation. The nearly spherical NiCoB nanoparticles, as-prepared by the chemical reduction of metallic salts, were amorphous according to previous study. The resulting MgB2 sample, formed after the sintering at 650 °C, was subjected to detailed microstructural analysis which included the application of various experimental methods: XRD, FE-SEM, EDS, elemental mapping, TEM and SAED. The methods confirmed the formation of new crystal CoNi phase (due to heat treatment at 650C), consisting of spherical nanoparticles (~ 6 nm) with tendency to spherical agglomerates formation. Those nanosized magnetic particles (characterized by the single domain magnetic structure and blocking temperature TB below room temperature), located at MgB2 grain boundaries, could serve as effective magnetic pinning centers in MgB2, thus improving its electromagnetic properties.

This work is licensed under a Creative Commons Attribution 4.0 International License.

Keywords

magnesium diboride; CoNi nanoparticles; X-ray diffraction; Rietveld refinement; scanning electron microscopy (SEM); transmission electron microscopy (TEM)

Hrčak ID:

182670

URI

https://hrcak.srce.hr/182670

Publication date:

2.1.2017.

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