Effect of sample size on magnetic Jc for MgB2 superconductor

Horvat, J.; Soltanian, Saeid; Wang, Xiaolin; Dou, Shi Xue

doi:10.1063/1.1713031

Cited by 30 publications

(34 citation statements)

References 11 publications

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“…Bar-shaped samples of about the same size were cut from the as-sintered pellets to minimize size-dependent effects. 5 Magnetic J c values were determined from the magnetization hysteresis loops using the appropriate critical state model. 6 An empirical magnetic irreversibility line, H M * , was defined as the field at which J c falls to 100 A / cm 2 .…”

Section: Methodsmentioning

confidence: 99%

Nanoscale-SiC doping for enhancing Jc and Hc2 in superconducting MgB2

Dou

Braccini

Soltanian

et al. 2004

Journal of Applied Physics

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130

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The effect of nanoscale-SiC doping of MgB 2 was investigated in comparison with undoped, clean-limit, and Mg-vapor-exposed samples using transport and magnetic measurements. It was found that there are two distinguishable but related mechanisms that control the critical current-density-field J c ͑H͒ behavior: increase of upper critical field H c2 and improvement of flux pinning. There is a clear correlation between the critical temperature T c , the resistivity , the residual resistivity ratio RRR= R͑300 K͒ / R͑40 K͒, the irreversibility field H*, and the alloying state in the samples. The H c2 is about the same within the measured field range for both the Mg-vapor-treated and the SiC-doped samples. However, the J c ͑H͒ for the latter is higher than the former in a high-field regime by an order of magnitude. Mg vapor treatment induced intrinsic scattering and contributed to an increase in H c2 . SiC doping, on the other hand, introduced many nanoscale precipitates and disorder at B and Mg sites, provoking an increase of ͑40 K͒ from 1 ⍀ cm ͑RRR= 15͒ for the clean-limit sample to 300 ⍀ cm ͑RRR= 1.75͒ for the SiC-doped sample, leading to significant enhancement of both H c2 and H* with only a minor effect on T c . Electron energy-loss spectroscope and transmission electron microscope analysis revealed impurity phases: Mg 2 Si, MgO, MgB 4 , BO x , Si x B y O z , and BC at a scale below 10 nm and an extensive domain structure of 2 -4-nm domains in the doped sample, which serve as strong pinning centers.

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Section: Methodsmentioning

confidence: 99%

Nanoscale-SiC doping for enhancing Jc and Hc2 in superconducting MgB2

Dou

Braccini

Soltanian

et al. 2004

Journal of Applied Physics

Self Cite

130

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“…Magnetization was measured from 5 to 30 K in magnetic fields up to 9 T using a 9 T Physical Property Measurement System (PPMS, Quantum Design). Bar-shaped samples of about the same size were cut from the as-sintered pellets to minimize size-dependent effects [9]. Magnetic J c values were determined from the magnetization hysteresis loops using the appropriate critical state model.…”

Section: Methodsmentioning

confidence: 99%

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

Dou

Soltanian

Zhao

et al. 2005

Supercond. Sci. Technol.

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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.

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“…The magnetic measurements were performed by applying the magnetic field perpendicular and parallel to the wire sample axis. Since there is a large sample size effect on the magnetic J c for MgB 2 [27,28] all the samples for measurement were made to the same size for comparison. The magnetic J c was derived from the width of the magnetization loop using Bean's model.…”

Section: Experimetalmentioning

confidence: 99%

Alignment of Carbon Nanotube Additives for Improved Performance of Magnesium Diboride Superconductors

et al. 2006

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The rapid progress on MgB 2 superconductor since its discovery [1] has made this material a strong competitor to low and high temperature superconductors (HTS) for applications with a great potential to catch the niche market such as in magnetic resonant imaging (MRI). Thanks to the lack of weak links and the two-gap superconductivity of MgB 2 [2,3] a number of additives have been successfully used to enhance the critical current density, J c and the upper critical field, H c2 . [4][5][6][7][8][9][10][11][12] Carbon nanotubes (CNTs) have unusually electrical, mechanical and thermal properties [13][14][15][16] and hence is an ideal component to fabricate composites for improving their performance. To take advantages of the extraordinary properties of CNTs it is important to align CNTs in the composites.Here we report a method of alignment of CNTs in the CNT/MgB 2 superconductor composite wires through a readily scalable drawing technique. The aligned CNT doped MgB 2 wires show an enhancement in magnetic J c (H) by more than an order of magnitude in high magnetic fields, compared to the undoped ones. The CNTs have also significantly enhanced the heat transfer and dissipation. CNTs have been used mainly in structural materials, but here the advantage of their use in functional composites is shown and this has wider ramifications for other functional materials.

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Effect of sample size on magnetic Jc for MgB2 superconductor

Cited by 30 publications

References 11 publications

Nanoscale-SiC doping for enhancing Jc and Hc2 in superconducting MgB2

Nanoscale-SiC doping for enhancing Jc and Hc2 in superconducting MgB2

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

Alignment of Carbon Nanotube Additives for Improved Performance of Magnesium Diboride Superconductors

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Effect of sample size on magnetic Jc for MgB2 superconductor

Cited by 30 publications

References 11 publications

Nanoscale-SiC doping for enhancing Jc and Hc2 in superconducting MgB2

Nanoscale-SiC doping for enhancing Jc and Hc2 in superconducting MgB2

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

Alignment of Carbon Nanotube Additives for Improved Performance of Magnesium Diboride Superconductors

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