Bi-2201, Bi-2212 and (Bi,Pb)-2223 fibers have been grown using the micro-pulling down (μ-PD) technique

Abstract

Many studies on various methods for growing crystals by methods including flux, self-flux, Bridgman, and floating zone growth have been carried out. Recently the micro-pulling down (μ-PD) method has been used to grow high-quality oxide fibers with minimal residual stresses, even incongruently melting compounds or high melting temperature materials. Thus, we thought to extend this technique to superconducting materials. In this work, the (Bi,Pb) 2Sr 2Ca n−1 Cu n O z superconductors fibers were successfully grown by the micro-pulling-down using a seeding technique and were of reasonable quality, as was proved by X-ray diffraction, scanning electron microscopy and SQUID measurements. The grown fibers had a regular shape with uniform diameter and different length which was limited only by the crucible size and quantities of starting materials. The fibers were composed of plate-like crystals, oriented along the pulling direction and were superconducting. Nearly pure-phase (more than 90%) Bi-2201 and Bi-2212 fibers could be obtained at pulling rates 0.08 mm/min, exhibit superconducting behaviour with critical temperature T c = 21 K and 90 K respectively with transition width (10–90% level) between 5 and 10 K. For (Bi,Pb)-2223 fiber obtained displays two superconducting transitions around 107 and 85 K, corresponding to 2223 and 2212 phases, respectively. Therefore the 2212 phase is the dominant phase in fiber grown.