Superconductivity in porous MgB2

Grinenko, V.; Krasnoperov, E. P.; Stoliarov, V A; Bush, A. A.; Mikhajlov, B P

doi:10.1016/j.ssc.2006.03.036

Cited by 19 publications

(12 citation statements)

References 23 publications

(35 reference statements)

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“…11 As the sample density was decreased, the measured onset critical temperature (T c,0 ) decreased, and the width of the superconducting transition increased significantly, indicating decreased connectivity between particles and decreasing the temperature range in which MgB 2 can be used as a useful superconductor. In addition, denser material can be expected to reach higher transport critical currents than porous material processed by the same method, as the cross-sectional area of superconducting material is higher for a given sample diameter.…”

Section: Introductionmentioning

confidence: 96%

A study of the sintering behaviour of magnesium diboride

Dancer

Mikheenko

Bevan

et al. 2009

Journal of the European Ceramic Society

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It is well known that a substantial increase in critical current density can be achieved by the heat-treatment of ex situ magnesium diboride powderin-tube wires. However, it is not clear whether this is due to a true sintering process involving the significant transport of material and densification, or due for instance to the removal of volatile impurities from particle interfaces, limited chemical reactions at particle boundaries, or simply contact formation between particles by thermally activated direct adhesion. We believe that the term sintering in the magnesium diboride literature may often be used loosely when neither neck formation nor densification occurs during heat-treatment, and have designed experiments to understand what is happening during this processing step. We have studied the effect of a range of heat-treatments on the microstructure of pellets produced from commercial MgB 2 powder using X-ray diffraction, scanning electron microscopy, Vickers hardness tests and by density measurements using Archimedes' principle. The results are compared to those from a dense sample produced from the same powder by resistive sintering. No significant densification is observed in pellets produced by conventional pressure-less heat-treatment up to 1100 • C. However, a clear correlation between density and hardness is established by comparison with results for bulk MgB 2 produced by resistive sintering, which confirms that a classical sintering process has been induced in the latter samples.

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Section: Introductionmentioning

confidence: 96%

A study of the sintering behaviour of magnesium diboride

Dancer

Mikheenko

Bevan

et al. 2009

Journal of the European Ceramic Society

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“…It is well known that the lattice parameters of MgB 2 decrease with the increasing porosity. 27 Both the lattice parameters a and c increase with the increasing Er concentration, as given in table 1. It is expected from these results that some Er atoms have partially substituted into MgB 2 , possibly at Mg sites.…”

Section: Methodsmentioning

confidence: 90%

Effect of Er doping on the superconducting properties of porous MgB 2

Erdem

Yanmaz

2015

Bull Mater Sci

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MgB 2 bulk sample with porous structure was produced by using the in-situ solid-state reaction method under argon (Ar) atmosphere of 10 bar. Elemental Er in powder form was doped into MgB 2 with different compositions (Mg 1−x Er x)B 2 , where x = 0.00, 0.03 and 0.05, in order to investigate the effect of rare-earth (RE) element Er on the structural and electromagnetic properties of porous MgB 2. The Er-doped samples result in small grain size structure compared to the undoped one. The lattice constants a and c of the doped samples, determined from X-ray diffraction (XRD) analysis, increase with the increasing Er content, and consequently the superconducting transition temperature (T onset c) of MgB 2 , determined from resistivity measurements, is slightly suppressed. Also, the upper critical field (B c2), the irreversibility field (B irr) and the critical current density (J c) values are significantly enhanced in the doped samples. For the best sample (x = 0.03), at 15 K under a magnetic field of 4 T, the J c value reaches 2.4×10 4 A cm −2 , which is higher than that of the porous sample by an order of 10 3 , and the B irr value at 20 K reaches 9.7 T. These results imply that the RE element Er fills the pores, enhances the density and the grain connectivity. Hence, the superconducting properties of the porous MgB 2 sample improve by Er doping. Keywords. Superconductivity; (Mg 1−x Er x)B 2 ; upper critical field; irreversibility field; critical current density.

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“…3 also reveals the presence of MgB 4 as reported elsewhere. 7,[21][22][23][24] According to the phase diagram of Mg-B system 25 at high temperature, the Mg vapour is present in equilibrium with MgB 2 or MgB 4 . On the other hand, the XRD of the sample processed at 1200 C shows more MgB 4 peaks.…”

Section: Resultsmentioning

confidence: 99%

“…But, this leads to low relative densities which affect the final properties of the materials. 7 Different methods have been used for densifying the material such as high pressure sintering, 8,9 hot isostatic pressing (HIP), 10,11 hot compaction, 12 and nonconventional Field Assisted Sintering Techniques (FAST) or Spark Plasma Sintering (SPS) process. [13][14][15][16][17][18] The main target of this work is to enhance the connectivity between grains in order to improve the sample properties.…”

Section: Introductionmentioning

confidence: 99%

Development in processing of MgB2 cryo-magnet superconductors

Noudem

Aburras

Bernstein

et al. 2014

Journal of Applied Physics

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Articles you may be interested inDependence of magnetoelectric properties on sintering temperature for nano-SiC-doped MgB2/Fe wires made by combined in situ/ex situ process J. Appl. Phys. 111, 07E135 (2012); 10.1063/1.3677660 Transport properties of superconducting MgB2 composites with carbon-encapsulated Fe nanospheresSpark Plasma Sintering is a promising rapid consolidation technique that allows a better understanding and manipulating of sintering kinetics and therefore makes it possible to obtain MgB 2 -based ceramics with tailored microstructures. Commercial MgB 2 powders were spark plasma sintered with an applied mechanical pressure, leading to MgB 2 pellets with 99% relative density. The obtained samples show a sharp superconducting transition with an onset at 38.5 K. The critical current density was measured equal to 5.6 Â 10 4 A/cm 2 at 20 K under 1 T applied field. Otherwise, the trapped field was also investigated. A 5 mm thick pellet with a 20 mm diameter prepared with optimized processing temperature demonstrated a trapped field of 1.2 T at 15 K and up to 2.5 T at 10 K. V C 2014 AIP Publishing LLC. [http://dx.

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Superconductivity in porous MgB2

Cited by 19 publications

References 23 publications

A study of the sintering behaviour of magnesium diboride

A study of the sintering behaviour of magnesium diboride

Effect of Er doping on the superconducting properties of porous MgB 2

Development in processing of MgB2 cryo-magnet superconductors

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