Significant enhancement of superconducting performances of Bi-2212 fibers through combined sodium substitution and LFZ process

Abstract

This paper reports the microstructure, magneto-resistivity, electrical and superconducting properties of Bi-2212 fibers with Na + ions incorporated into a superconducting matrix prepared by a polymer solution method and additionally textured through the laser floating zone process. XRD patterns showed that Bi-2212 phase is the major one with mostly (00ℓ) diffractions due to the grain alignment, independently of Na content. SEM micrographs showed that samples are composed of well-stacked and oriented grains. The irreversibility field (Hirr), upper critical magnetic field (H c2 ), coherence length (ξ), and activation energies (U) have been calculated using magneto-resistivity measurements and explained based on the thermally activated flux flow (TAFF) model. Considering the resistivity-temperature graph for zero field, T c values tend to increase from 84.8 K (for the pure sample) to 93.2 K (for 0.075Na sample), slightly decreasing for higher content. Besides, transition temperature width (ΔT c = T c onset -T c offset ) decreases with the increment in the Na content and reaches its minimum value (ΔT c =3.7 K) in 0.075Na sample. However, broadening of superconducting transition has been observed with applied field and T c values decreased to 76.1 K for the pure sample and 86.8 K for 0.075Na sample. Likewise, the activation energies of the samples also decreases significantly with the increase of the magnetic field and the activation energies of the Na-containing samples are found to be higher than the pure sample at each magnetic field value. H c2 (0) values are calculated as 33.8, 43.8, 50.1, 33.1, and 21.4 T for 0.0, 0.075, 0.10, 0.20 T Na samples, respectively. As a consequence, referring to all experimental results and theoretical findings, the superconducting characteristics improve regularly with Na-doping until x=0.075 due to increment in the interaction of superconducting clusters, decrement in weak-links and stabilization of charge-carriers in CuO 2 conducting planes.

Investigation of the structural and electrical properties of CdO/(Bi, Pb)−2212 superconducting phase

“…Such enhancement of the transport properties allowed the utilization of the (Bi, Pb)−2212 phase in the production of high-temperature superconducting nanowires [7], suggesting them as favorable candidates for power transmission cables. On the other hand, a major drawback of the (Bi, Pb)−2212 superconductors is the relatively low superconducting transition temperature (T c ) as compared to the T c of the(Bi, Pb)−2223 superconductor [8]. Various methods were utilized to enhance the T c of (Bi, Pb)−2212 phase, including elemental substitution or addition of nano-sized particles to the superconducting phase.…”