Transport Properties of Melt-Cast-Processed Bi-2212 Bulk Superconductor Bars

Abstract

Bulk materials of high-critical-temperature superconductors (HTSs) are promising for current leads and faultcurrent limiters because of negligibly small Joule heating under current transport and very low thermal conductivity. We consider that a Bi-2212 bulk superconductor prepared by the melt-casting process (MCP) is one of the best materials for these applications. In addition, MCP is well known to be a simple and economic process, and also served as a method for obtaining any sizes of HTS bulks consent to requirements for practical applications. In this paper, we present a study on the transport and quench properties of Bi-2212 bulk superconductors doped with K 2 CO 3 . First, the MCP samples doped with K 2 CO 3 were analyzed by using an X-ray diffractometer and X-ray fluorescence spectrometry. In addition, the critical temperatures of the MCP samples doped with K 2 CO 3 were observed. Then, we have investigated the relations between the critical current value and the doping quantity of K 2 CO 3 . The value of the direct-current critical current was determined at 77 K, and the self-fields derived from the electric field versus the transport current characteristics were obtained using a criterion of 1 μV/cm. Finally, the alternating-current transport properties of the MCP sample were measured, and we have discussed the frequency dependence of the critical current with current distributions.

Anisotropy of the thermal conductivity of bulk melt-cast Bi-2212 superconducting tubes

“…Whatever the reason, the origin of this foot will not be discussed further. The resistivity values are comparable to those measured along the axis of bulk melt-cast Bi-2212 bars [29]. The anisotropy behavior depicted in figure 3 qualitatively agrees with results obtained on similar samples [21] in that the normal-state resistivity ratio ρ(axial,azimuthal) / ρ(radial) is very weakly temperature dependent with an average value equal to ~ 1.5, which is smaller than the ratio ~ 2.3 found by Dellicour et al [21] for a similar tube of other dimensions (wall thickness ~7.5 mm) and, thus, different solidification microstructure.…”