Physical, electrical and magnetic properties of Cr doped Bi2Sr2Ca1Cu2−xCrxOy (Bi-2212) superconductors prepared by laser floating zone technique

Abstract

The structural and magnetic properties evolution of Cr-doped Bi 2 Sr 2 CaCu 2-x Cr x O y ceramics (x= 0.0, 0.05, 0.1, and 0.25) have been investigated using XRD, SEM, DC resistivity and M-H measurements. X-ray diffraction studies have shown that all samples are mainly composed of Bi-2212 phase, indicating that Cr can be incorporated in its crystal structure. The microstructure of the highly Cr-doped samples showed that some impurity phases appear, decreasing the conductivity between the grains. T c (onset) and T c (offset) have been improved for x=0.05 Cr doping, while 0.25 Cr doped samples are not superconducting. This behavior can be associated to changes in the hole concentration and/or the magnetic nature of Cr. The magnetic properties indicate that low Cr-doping enhances the loop widths. Additionally, the critical current densities, J c , of samples have been calculated by using the Bean's critical state model. It has been found that there are important improvements in J c values between 0.2-0.9 T applied magnetic fields for 0.05 Cr doped samples.