Enhanced higher temperature irreversibility field and critical current density in MgB₂ wires with Dy₂O₃ additions

Abstract

Bulk samples of magnesium diboride (MgB2) doped with 0.5 wt% of the rare earth oxides (REOs) Nd2O3 and Dy2O3 (named B-ND and B-DY) prepared by standard powder processing, and wires of MgB2 doped with 0.5 wt% Dy2O3 (named W-DY) prepared by a commercial powder-in-tube processing were studied. Investigations included x-ray diffractometry, scanning- and transmission electron microscopy, magnetic measurement of superconducting transition temperature (T c), magnetic and resistive measurements of upper critical field (B c2) and irreversibility field (B irr), as well as magnetic and transport measurements of critical current densities versus applied field (J cm(B) and J c(B), respectively). It was found that although the products of REO doping did not substitute into the MgB2 lattice, REO-based inclusions resided within grains and at grain boundaries. Curves of bulk pinning force density (F p) versus reduced field (b = B/B irr) showed that flux pinning was by predominantly by grain boundaries, not point defects. At all temperatures the F p(b) of W-DY experienced enhancement by inclusion-induced grain boundary refinement but at higher temperatures F p(b) was still further increased by a Dy2O3 additive-induced increase in B irr of about 1 T at all temperatures up to 20 K (and beyond). It is noted that Dy2O3 increases B irr and that it does so, not just at 4 K, but in the higher temperature regime. This important property, shared by a number of REOs and other oxides promises to extend the applications range of MgB2 conductors.

Antimicrobial Activity of MgB2 Powders Produced via Reactive Liquid Infiltration Method

“…Sample MBNB02 has hexagonal-shaped plate-like grains about 1 µm in size with sharp edges and almost clear surfaces (see Figure 3f, blue contours). This hexagonal plate-like morphology of MgB2 grains is frequently reported in the literature [44][45][46]. However, on a larger scale, the same sample shows the abundant presence of lumpy spherical aggregates approximately 5 µm in diameter (see Figure 3d).…”

Correlation between microstructure and superconducting properties of MgB2 bulk samples with Mg addition and Mg/hBN co-additions

“…It is widely accepted that localized lattice strains caused by carbon substitution for boron in the MgB 2 lattice increase H c2 and intrinsic J c at the cost of a significant decrease in T c [19,20]. Rare earth oxide nanoparticle additions with a size comparable to the coherence length of MgB 2 (∼10 nm) are found to be effective in strengthening flux pinning and enhancing intrinsic J c [13,21,22]. The addition of low melting point metals can lower the sintering temperature and improve the extrinsic connectivity of the MgB 2 particles by encouraging liquid phase sintering [15,16,23,24].…”

Effects of irradiation on superconducting properties of small-grained MgB2 thin films

“…[6] Therefore, a kilometer-long MgB 2 superconducting wire used in real systems can be fabricated using a simple powder-in-tube technique, thus considerably reducing the manufacturing cost. [7,8] The high current-carrying capability for superconductors necessary for practical applications in magnetic field environment can be achieved by introducing artificial defects. [9] Particle irradiation is a suitable method for producing defects in superconducting materials and has been successfully used in roll-to-roll 80-m long YBa 2 Cu 3 O 7−δ coated conductors.…”