Superconducting and normal state properties of the Bi1.7Pb0.3Sr2Ca2 − xYxCu3Oy system

The superconducting and normal state properties of the Bi1.7Pb0.3Sr2Ca2 − xYxCu3Oy (0.0 ≤ x ≤ 0.1) system were studied by various techniques. The structural analysis was carried out by XRD and the results have revealed the conversion of the major (2223) phase to (2212) with Y substitution. The solubility limit of Y in the BISCCO (2223) system was found to be around x = 0.02. The granular nature of superconductivity in the compounds was evident from AC susceptibility results. Samples with higher Y contents have shown a two step inductive transition indicating the presence of the two phases. The thermoelectric power measurements have shown that Y substitution decreases the hole carrier concentration both in the (2223) and (2212) phases with an increased electron phonon interaction at low temperatures. The transition temperatures measured from TEP are more than that from resistivity measurements. This may be owing to the higher percolation concentration needed to observe zero resistivity when compared with the percolation concentration for zero TEP.