Flux pinning and microstructure of a bulk MgB2doped with diverse additives

M. Jirsa, M. Rameš, M. Miryala, P. Svora, J. Duchoň, O. Molnárová, S. S. Arvapalli, M. Murakami

研究成果: Article査読

抄録

In bulk high-temperature superconductors, Ag is usually used as an additive thus improving mechanical performance. In MgB2 doped with Ag, the Ag reacts with Mg, forming Mg-Ag phases acting as a vortex pinning medium. In this work, we analyze the electromagnetic and pinning properties of bulk MgB2 doped with 1 wt% MgB4, 4 wt% Ag, and 1 wt% Dy2O3, prepared at the Shibaura Institute of Technology (SIT), Tokyo. In three compounds of MgxB2 + 4 wt% Ag with x = 1, 1.075, and 1.1, the effect of Mg excess was studied. The magnetic moment was measured by a vibrating sample magnetometer (VSM). Pinning was studied in terms of a pinning diagram, i.e. the field dependence of the normalized pinning force density, F n = F/F max. In all studied samples, the peak of the F n (b) dependence (b= B/B irr, B irr being the irreversibility field) was observed at around b= 0.2, indicating a prevailing flux pinning at grain boundaries. A slight shift of the peak with decreasing temperature indicated a defect size distribution in the pinning landscape. Transmission electron microscopy (TEM) showed a granular structure of all samples composed of MgB2 grains of about 230 nm (average size), with ensembles of small grains (22 nm in average) of Ag3Mg, AgMg, Ag, Dy2O3, and MgB4. While the large MgB2 grains control the main pinning mechanism, the small precipitates seem to determine details of the current flow through the grain boundaries.

本文言語English
論文番号094007
ジャーナルSuperconductor Science and Technology
33
9
DOI
出版ステータスPublished - 2020 9

ASJC Scopus subject areas

  • セラミックおよび複合材料
  • 凝縮系物理学
  • 金属および合金
  • 電子工学および電気工学
  • 材料化学

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