Effect of K substitution on Structural, Electrical and Magnetic Properties of Bi-2212 system.

In this work, the effect of K in the BiSrCaKCuO superconductor with x = 0.0, 0.05, 0.075, and 0.1, has been investigated. The samples were prepared by a polymer solution technique using polyethyleneimine, PEI. The effects of K substitution have been investigated by electrical resistivity ( ρ− T), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy, and magnetic characterizations. SEM and XRD results have shown that the Bi-(2212) phase is the major one independently of the K concentration. Moreover, the microstructure of samples is improved with K-concentration up to x = 0.075. From electrical resistivity measurements we have found that Tc is slightly higher than 91 K for K-concentrations up to 0.075, and then it decreases for higher doping for about 0.5 K. Moreover, this trend is maintained in the magnetic measurements in which the hysteresis loops are increased until 0.075 K-concentrations. The maximum calculated Jc, using Bean's model, has been found at around 4.5 10A/cm at 10 K and ~1,000 Oe for the 0.05 K doped samples. [ABSTRACT FROM AUTHOR]