Effect of Yb Substitution in Bi sub(1.6) Pb sub(0.4) Sr sub(2) Ca sub(2-x) Yb sub(x) Cu sub(3) O sub(y) Superconductor

This paper reports on the results of Yb substitution for Ca on the superconductivity and structural properties of Bi sub(1.6) Pb sub(0.4) Sr sub(2) Ca sub(2-x) Yb sub(x) Cu sub(3) O sub(y) superconducting samples with x = 0.000, 0.025, 0.050, 0.100 and 0.200 which prepared by coprecipitation (COP) method. The samples were characterized by X-ray diffraction (XRD), field-emission scanning electron (FESEM), electrical and resistivity measurement by four-probe method. It was found that the substitution of Yb decreased the critical temperature (T sub(c zero)), critical current density (J sub(c)) and volume fraction of Bi-2223 phase. The samples have T sub(c zero) in the range 77 to 100 K. T sub(c zero) gradually decreased with an increase in Yb concentration, corresponding to small change of the carrier concentration. J sub(c) was measured to be 5.7512 A/cm super(2) for pure sample and decreased to 4.1910 A/cm super(2) for x = 0.025 at 77 K. The crystallographic structure was found to change slightly from tetragonal to orthorhombic in Yb substituted samples. The lattice parameter c of Yb samples decreased due to the incorporation of Yb super(3+)(0.858 A) with smaller ionic size compare to Ca super(2+)(0.99 A). From the SEM observation, the grain connectivity became weak with smaller plate-like grain for x > 0.025 Yb concentration resulting in the decreased of J sub(c).