Effects of intergrain and intragrain currents on flux profile in granular superconducting ceramics

Zeitschrift für Physik B Condensed Matter

et al. 1996

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Abstract:We measured the AC susceptibility of magnetically textured (123) 80%/211(20%) DyBaCuO composite in a special set-up in order to enhance the intergrain contribution. The synthesis process led to very clean "weak links" at grain boundaries. At the percolation threshold bulk shielding paths were such that the intergrain critical current density J C was above 10 5 A/cm 2 . The field dependence of J C was understood through an analytical form indicating a distribution of currents similar to the law of clusters at fracture/percolation thresholds.

Section: Electrical and Magnetic Investigations Of The Intragranular mentioning

confidence: 99%

Field percolation and high current density in 80/20 DyBa2Cu3O7 − x/Dy2BaCuO5 bulk magnetically textured composite ceramics

Cloots

Dang

Zeitschrift für Physik B Condensed Matter

et al. 1996

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“…Because λ is not negligible with respect to the mean grain radius, the grain proportion is then underestimated. Following a Bean model generalization [14], the slope of the flux profiles at low field amplitudes is proportional to the intergranular current density J c . Experimental data (figure 7) clearly show that J c is strongly affected by the applied DC magnetic field.…”

Section: Campbell-rollins Methodsmentioning

confidence: 99%

Magnetic flux penetration and creep in BSSCO-2223 composite ceramics

Supercond. Sci. Technol.

Destombes

Cloots

et al. 1998

Abstract. We have experimentally investigated the magnetic flux penetration through a Bi-2223 polycrystalline superconductor synthesized by a classical solid-state reaction method. Electrical resistance, AC susceptibility, the Campbell method and magnetic flux waveform recordings have been analysed and compared in order to separate clearly intergrain and intragrain contributions. The AC susceptibility frequency dependence has been also examined at T = 77 K in a broad field range (0.01 G< B AC < 100 G). The activation energy as a function of AC applied magnetic field is found to present a pronounced minimum for an induction (8 G) corresponding to full magnetic flux penetration through the intergranular matrix.

“…Usually a shoulder is predicted when weak links are present. This shoulder generally allows to deduce both intergranular (J cj ) and intragranular (J cg ) critical current densities from the slopes of the flux profile on both sides of the shoulder [4][5][6]. This is not the case here, where flux profiles are rather linear.…”

Section: Flux Profilesmentioning

confidence: 97%

AC susceptibility data on Dy2O3 seeded randomly oriented Dy-123 mono domains melt-textured superconductor

Materials Science and Engineering: B

Bougrine

Ausloos

et al. 1998

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Dy-123 superconducting ceramics have been grown using small Dy 2 O 3 single-crystals as seeds. Randomly oriented large mono-domains have been observed in the vicinity of the seeding single crystal. These domains are one order of magnitude greater in volume than the seed. The AC susceptibility versus temperature curves have been measured in a polycrystalline cubic sample for different orientations of the magnetic field with respect to the sample and for amplitudes up to 20 G. Three measuring coils, each parallel to one side of the sample, were used to investigate the anisotropy of the properties. Electrical resistance versus temperature and flux profiles at 77 K were also explored. The results show good grain connectivity. A non negligible part of the magnetic shielding is due to currents flowing inside the grains.