Transport behavior and critical current densities in MgB2 wires

Abstract

We report on the transport and magnetization properties of MgB2 wires fabricated by a powder-in-tube (PIT) technique. Temperature and magnetic-field-dependent resistivity displays a high conductivity and upper critical field Hc2 generally observed in dense samples. The electronic mass anisotropy γ≈1.3±0.15 predicts some texturing in the wire. Our data on transition temperature TC, Hc2, and both magnetic and transport critical current density Jc indicate that MgB2 can be manufactured in a wire form using a PIT technique and required engineering Jc can be achieved on further optimization.

Fabrication and superconducting properties of MgB2composite wiresby the PIT method

“…In addition, Canfield et al [11] fabricated high-density MgB 2 wires (160 µm in diameter) through the exposure of boron filaments to Mg vapour. Also, many results have been published on PIT MgB 2 tapes and wires [12][13][14][15]. In this paper, we report a simple method to prepare MgB 2 /Cu wires with a Ta buffer layer and the results of the magnetization measurements and the critical current densities and irreversibility fields that are deduced from the hysteresis loops.…”

High critical current density and improved irreversibility field in bulk MgB2 made by a scaleable, nanoparticle addition route

“…In slightly more than one year after the discovery of superconductivity in magnesium diboride, there is now a wide body of evidence indicating that MgB 2 does not contain intrinsic obstacles to current flow between grains, unlike the high-temperature superconducting cuprates. Evidence for strongly coupled grains has been found even in randomly aligned, porous, and impure samples, 1,2 suggesting that dense forms of MgB 2 will be attractive in high-current applications at 20-30 K and perhaps 4.2 K. So far, however, bulk samples have demonstrated modest values of the irreversibility field 0 H*(T) reaching about 4 T at 20 K and 8 T at 4.2 K. 3 For comparison, established low-temperature superconductors, e.g., NbTi ͑10 T͒ and Nb 3 Sn ͑20 T͒, have significantly higher irreversibility fields at 4.2 K, while Bi 2 Sr 2 Ca 2 Cu 3 O 10 ͑3 T͒ is becoming established at 20 K. 4 MgB 2 tape results are somewhat more promising, with 0 H* values of above 5 at 20 K, [5][6][7][8] where partial orientation of crystallites parallel to the field is playing a role. Since the irreversibility field is the practical limit to magnet applications, it is desirable to make 0 H* values as high as possible.…”

Electrical transport properties of bulk MgB2materials synthesized by electrolysis on fused mixtures of MgCl2, NaCl, KCl and MgB2O4

“…Electrical resistivity measurements for the grown deposits show an onset of superconducting transition at ~37 K in the absence of applied magnetic field. The resistivity decreases down to zero below ~32 K. From an applied-field dependence of resistivity, an upper critical field and a coherence length were calculated to be 9.7 T and 5.9 nm at 0 K, respectively.Recent discovery of superconductivity in MgB 2 at a transition temperature (T C ) as high as 39 K [1] has shown a possibility of new superconducting materials for low-cost and high-performance electrical devices and magnets [2][3][4][5][6][7][8][9][10][11][12][13][14]. This transition temperature much exceeds the highest value of binary intermetallic compounds, T C =23 K for the A15-type compound Nb 3 Ge [15].…”

“…Only the high-T C cuprates and alkaline-doped C 60 are known to have the comparable order of T C values [16]. From the viewpoint of industrial application, wires [3,11], tapes [12] and thin films [13] as well as bulk samples [9,10,14] were fabricated by means of direct reactions between elemental Mg and B.The present authors have recently proposed an electrochemical synthesis method of MgB 2 [17]. Black deposits containing MgB 2 were obtained by means of electrolysis on a fused mixture of MgCl 2 , KCl and MgB 2 O 4 with a molar ratio of 5:5:1 (denoted as KCl-bath for brevity hereafter) at the temperatures lower than the melting point of Mg, 651°C.…”

“…Only the high-T C cuprates and alkaline-doped C 60 are known to have the comparable order of T C values [16]. From the viewpoint of industrial application, wires [3,11], tapes [12] and thin films [13] as well as bulk samples [9,10,14] were fabricated by means of direct reactions between elemental Mg and B.…”