Effect of V substitution on vortex pinning and superconducting properties of Bi-2212 superconductor

In this work, the effect of Vanadium (V) substitution in the Bi2Sr2Ca1−xVxCu2O8+y superconductor with x = 0.0, 0.05, 0.1, 0.2, 0.3, and 0.4 has been investigated. The samples were prepared by a conventional solid state reaction technique. The effects of vanadium substitution have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, and magnetic characterizations. XRD patterns indicate that the Bi-(2212) phase is the major one for pure sample, but with increasing of V content, the volume fraction of Bi-2212 is reduced and transformed to mainly low-Tc phase, namely Bi-2201. 0.05 V substitution causes a remarkable increase of superconducting critical temperature as 86.2 K, which is higher than pure sample by 2.3 K. Moreover, 0.05 V leads to improvement of intragranular JC value which is calculated as 2.53 × 104 A/cm2 at 10 K. For comparison, the enhancement in JC value is about 78 % more than those value obtained for pure sample. The whisker structure with a length of 0.25 mm in main matrix is also observed in the SEM micrographs of 0.4 V substitution.