Overview of spark plasma synthesis and sintering of MgB₂ superconductor

Abstract

This study aims to investigate the flash sintering mechanisms of magnesium diborides using SPS and optimize the sintering process conditions. Three different precursor materials were used: i) commercial powder MgB2, ii) mixtures of magnesium and nano boron powder (Mg + 2B), and iii) mixtures of Mg and MgB4 powder for an "in-situ" reactive synthesis. The density of the obtained bulks exceeds 90 % of the theoretical density of the material. The structure and microstructure of the samples were analyzed using X-ray diffraction and SEM, which were correlated with their superconducting properties. The critical current density (Jc), pinning force (fp), and electrical resistivity (ρ) of the samples were also investigated. The results show that the in-situ reactive synthesis of MgB2 using magnesium and nano boron powder was the most effective method for producing high-quality samples with improved superconducting properties. The findings could lead to the development of more efficient methods for producing high-performance of MgB2 bulks.

Comparison of the Field Trapping Ability of MgB2 and Hybrid Disc-Shaped Layouts

“…The MgB 2 sample was fabricated utilizing the spark plasma sintering system (FCT Systeme GmbH, HD25, Rauenstein, Germany), which is recognized as one of the most efficient technologies for dense MgB 2 bulk fabrication [ 27 ]. The sample was obtained by ex situ procedure using commercial MgB 2 powder (purity >97%, 100 meshes) purchased from PAVEZYUM Advanced Chemicals, Turkey.…”

“…The sample was obtained by ex situ procedure using commercial MgB 2 powder (purity >97%, 100 meshes) purchased from PAVEZYUM Advanced Chemicals, Turkey. The sample was sintered at 1200 °C for 10 min, allowing the production of a highly dense sample [ 27 ], while applying an axial pressure of 50 MPa under a dynamic vacuum of bar. The relative density of the sample was 2.6 g/cm 3 , corresponding to 99% of the theoretical value.…”

“…Studies indicated that the homogeneity and density of the superconducting MgB 2 material and the density of pinning centers can be improved by thermal treatment under high isostatic pressure or by an increase of the density of the MgB 2 material before the synthesis reaction [ 23 , 24 , 25 ]. Spark plasma sintering (SPS) is another technique that allows for the preparation of dense and large MgB 2 samples with a short process time [ 26 , 27 ]. By way of example, trapped field values of 2.12 T were achieved at 5 K (measured above a disc-shaped sample with a radius R = 9 mm and a height h = 6 mm) [ 28 ], 2.4 T at 15.9 K (measured above a disc-shaped sample with R = 15 mm and h = 6.6 mm) [ 29 ], and 3.2 T at 15 K (measured above a disc-shaped sample with R = 10 mm and h = 1.6 mm) [ 30 ].…”

“…In this work, the field-trapping ability of a MgB 2 disc grown using the spark plasma sintering (SPS) technique [ 26 , 27 , 50 ] was experimentally investigated at different working temperatures T = 20, 25, and 30 K. After the field cooling (FC) process, the magnetic flux density was measured by means of cryogenic Hall probes located along the sample diameter, and these were taken for different values of the external applied field and as a function of the distance from the disc surface. The possibility of enhancing the trapped field values via a ferromagnetic bulk addition was then studied by employing a numerical approach in order to avoid untargeted and time-consuming experimental trials.…”

Very strong levitation force and stability achieved with a large MgB2 superconductor disc

“…But, the as-processed samples show some porosities. Compared to the other techniques, SPS shows a great potential for preparing the highly dense and largesize superconductors in a short time while controlling their microstructure [19][20][21]. The simplicity of the fabrication process, coupled with their levitation force comparable to those of cuprate superconductors [9], highlights the enormous potential of this material for SML systems.…”