Study of Effect of PbO Addition in Bi₂Sr₂La_xCa_1 − xCu₂O_8+δ Ceramics

In this work, two seris samples of superconducting compounds of Bi₂Sr₂Ca_1-xLa_xCu₂O_8+δ  and Bi_1.95Pb_0.05Sr₂Ca_1-xLa_xCu₂O_8+δ, with different values of (x = 0, 0.01, 0.02, and 0.03), were successufully synthesized by using sol-gel method and then they were characterized by X-ray diffraction, scanning electron, and electrical transport. Ashift in the peaks can be observed in both series when the La content increases, which means a change in the lattice parameters. The SEM photographs show a noticeable change in the grain morphology for the lanthanum substituted samples as compared to undoped sample. The variation of resistivity with temperature for all of the samples exhibit a metallic-like character in the normal state, and increases in the broadening of the superconducting transition indicating an effect on the homogeneity of the samples. The increases in Tc are explained to be due the substitution of La³⁺ in place of Ca²⁺ with a consequent change in carrier concentration in the CuO₂ planes.