Improvement of structural and superconducting properties of Bi-2212 textured rods by substituting sodium

In this paper, the physical and superconducting properties of Bi2Sr2Ca1−xNaxCu2O8+δ with x=0.0, 0.05, 0.075, 0.1, and 0.20 textured superconducting fiber rods prepared by a laser floating zone (LFZ) technique were studied. The effects of Na+1 substitution for Ca2+ have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transport measurements, dc-magnetization, magnetic hysteresis and magnetic critical current density. The powder XRD patterns of samples have indicated that Bi-2212 phase is the major one, independently of Na content. The best critical temperature, TC, has been found as 93.3 K from M-T data for the sample with 0.075 Na substitution. The maximum magnetic JC value has been calculated as 1.35×105 A/cm2 at 10 K for the 0.10 Na sample. The maximum transport critical current density has directly been measured as 1.3×103 A/cm2 at 77 K for the 0.05Na sample.