Abstract
Abstract
Seven MgB2 bulk superconductors with good superconductivity and crystallinity were prepared under the pressure of 50 MPa at 950 °C and different sintering durations (15 ∼ 240 min) by spark plasma sintering (SPS), with the onset critical temperature (T
c,onset) around 37.5 K. The superconducting properties and microstructure measured from the facets perpendicular (PeF) and parallel (PaF) to the compression direction of the SPSed MgB2 bulk samples were also analyzed to investigate the effect of the sintering duration on the MgB2 bulks and the discrepancy between the PeF and the PaF. The optimum performance was obtained from the sample prepared for 45 min for both facets, and the critical current density (J
c) measured from the PeF and the PaF are 364 kA cm−2 and 344 kA cm−2 in self field at 20 K, respectively. The PeF exhibits better Jc
performance than the PaF at low fields and the PaF exhibits better J
c performance than the PeF at high fields. It can be concluded that the sintering duration affects the properties of the PeF mainly by changing their crystallite size. While for the PaF, the sintering duration mainly affects the microstructural defects, such as cracks, pores and secondary phase particles, thus further affecting their J
c performances. In terms of the flux pinning mechanism of the SPSed MgB2 bulk samples, the PaF is less susceptible to sintering duration than the PeF, and the better J
c performance of the PaF at high fields is due to the stronger grain boundary pinning. It can be also found that the point pinning being stronger at higher temperature is the result of the decreasing anisotropy of MgB2 bulk samples with the temperature.
Funder
the National Natural Science Foundation of China
the Shanghai Natural Science Foundation, China
the Innovation Program of Shanghai Municipal Education Commission, China
the Scientific Research Starting Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China
Subject
Materials Chemistry,Electrical and Electronic Engineering,Metals and Alloys,Condensed Matter Physics,Ceramics and Composites
Cited by
10 articles.
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