AC-susceptibility and transport phenomena of (Bi;Pb):2223 superconductors doped with rare earth ions

The effect of partial substitution of Ca by Eu, Sm and Er on the structural, transport and magnetic properties of (Bi_1.6Pb _0.4)Sr₂(Ca_1-xRE_x)₂Cu ₃O_y superconductors ceramics (0 ≤ x ≤ 0.025) have been investigated. The substitution of Eu, Sm and Er at the Ca site induced the decrease of the volume fraction for the 2223 phase and the increase of 2212 and 2201 phase volume fractions. The rate of depression for the critical temperature in x = 0.015 samples found to be nearly the same for all of these substitutions. The nature of T_c suppression may be attributed to the increase of oxygen content in Bi₂O₂ double layers with increasing Eu, Sm and Er concentrations. The samples shows a linear dependence of intergranular temperature as a function of AC field amplitude, which is in agreement with Muller critical state model.