Improved critical current properties observed in MgB₂ bulks synthesized by low-temperature solid-state reaction

Abstract

MgB2 bulks were synthesized by the solid-state reaction of Mg and B at 600 °C and their superconducting properties were compared with samples heated at 850 °C. The samples heated at 600 °C exhibited improved critical current properties up to high fields at 20 K. Poor crystallinity is found to contribute enhancement of Hc2, Hirr and Jc at high fields. On the other hand, the strongly grain connected network structure and smaller grain size are responsible for high Jc at low fields. Improved Jc up to 3.93 × 105 A cm−2 and a high μ0Hirr of T, as for undoped MgB2 bulks, guarantees that low-temperature sintering is a promising way to fabricate MgB2 conductors with high critical current performance.

The effect of doping level and sintering temperature on Jc(H) performance in nano-SiC doped and pure MgB2 wires

“…At low fields the J c values for the 10 and 15 wt % SiC doped wires are lower than those for the undoped samples at both 5 and 20 K. As it was shown in previous studies, SiC doping deteriorated J c values at low field regions. 2,13,17 According to x-ray diffraction ͑XRD͒ results ͑not shown; see, e.g., Ref. 12͒, the main impurity in studied SiC doped samples was Mg 2 Si, which increased with increasing doping level, but decreased with increasing sintering temperature.…”

“…[7][8][9][10][11][12][13][14][15][16][17][18] However SiC doping was found to have some negative effect on J c in the low field region. The J c for SiC doped MgB 2 was lower than that for undoped MgB 2 below 4 T at 5 K and below 2.5 T at 20 K. 2,13,17 There are many applications in the low field region such as in open magnetic resonance imaging ͑MRI͒ transformers and electric cables which normally operate at around 1-3 T. Thus it is important that the enhancement of J c by SiC doping can be extended to include all the field regions. In this Letter we report the results of the improved J c of SiC doped MgB 2 wires in all fields and temperature ranges.…”

Effects of heat treatment temperature on the formation of MgB2 bulk superconductors prepared using MgB4 and Mg powder

“…There are two different methods that can be used to fabricate MgB 2 : an ex-situ process [5][6][7][8] and an in-situ [9][10][11][12]. In the ex-situ process MgB 2 powder was used as a precursor [5][6][7][8].…”

Effects of the size of Mg powder on the formation of MgB2and the superconducting properties

“…MgB 2 superconductors can be fabricated either by an ex-situ process or an in-situ process [5][6][7][8][9][10][11][12]. In the ex-situ process, readily synthesized MgB 2 powder is used as a raw material [5][6][7][8], whereas in the in-situ process a powder mixture of Mg and B is used [9][10][11][12].…”

“…In the ex-situ process, readily synthesized MgB 2 powder is used as a raw material [5][6][7][8], whereas in the in-situ process a powder mixture of Mg and B is used [9][10][11][12]. The ex-situ processed MgB 2 superconductors showed a higher density with a small number of pores and excellent mechanical properties [6][7].…”