Electric transport measurements on bulk, polycrystalline MgB2 samples prepared at various reaction temperatures

A. Wiederhold, Michael Rudolf Koblischka, Kazuo Inoue, Muralidhar Miryala, Masato Murakami, U. Hartmann

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Abstract

A series of disk-shaped, bulk MgB2 superconductors (sample diameter up to 4 cm) was prepared in order to improve the performance for superconducting super-magnets. Several samples were fabricated using a solid state reaction in pure Ar atmosphere from 750 to 950oC in order to determine the optimum processing parameters to obtain the highest critical current density as well as large trapped field values. Additional samples were prepared with added silver (up to 10 wt.-%) to the Mg and B powder. Magneto-resistance data and I/V-characteristics were recorded using an Oxford Instruments Teslatron system. From Arrhenius plots, we determine the TAFF pinning potential, U 0. The I/V-characteristics yield detailed information on the current flow through the polycrystalline samples. The current flow is influenced by the presence of pores in the samples. Our analysis of the achieved critical currents together with a thorough microstructure investigation reveals that the samples prepared at temperatures between 775°C and 805°C exhibit the smallest grains and the best connectivity between them, while the samples fabricated at higher reaction temperatures show a reduced connectivity and lower pinning potential. Doping the samples with silver leads to a considerable increase of the pinning potential and hence, the critical current densities.

Original languageEnglish
Article number012004
JournalJournal of Physics: Conference Series
Volume695
Issue number1
DOIs
Publication statusPublished - 2016 Mar 17

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critical current
temperature
silver
current density
magnets
plots
solid state
porosity
atmospheres
microstructure

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

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title = "Electric transport measurements on bulk, polycrystalline MgB2 samples prepared at various reaction temperatures",
abstract = "A series of disk-shaped, bulk MgB2 superconductors (sample diameter up to 4 cm) was prepared in order to improve the performance for superconducting super-magnets. Several samples were fabricated using a solid state reaction in pure Ar atmosphere from 750 to 950oC in order to determine the optimum processing parameters to obtain the highest critical current density as well as large trapped field values. Additional samples were prepared with added silver (up to 10 wt.-{\%}) to the Mg and B powder. Magneto-resistance data and I/V-characteristics were recorded using an Oxford Instruments Teslatron system. From Arrhenius plots, we determine the TAFF pinning potential, U 0. The I/V-characteristics yield detailed information on the current flow through the polycrystalline samples. The current flow is influenced by the presence of pores in the samples. Our analysis of the achieved critical currents together with a thorough microstructure investigation reveals that the samples prepared at temperatures between 775°C and 805°C exhibit the smallest grains and the best connectivity between them, while the samples fabricated at higher reaction temperatures show a reduced connectivity and lower pinning potential. Doping the samples with silver leads to a considerable increase of the pinning potential and hence, the critical current densities.",
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AU - Wiederhold, A.

AU - Koblischka, Michael Rudolf

AU - Inoue, Kazuo

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AU - Murakami, Masato

AU - Hartmann, U.

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