Effect of Pb doping in high-T-c Bi2Sr2CaCu2Oy superconductors studied by X-ray absorption near-edge structure spectroscopy

An investigation of the variation of hole concentration within the CuO2 pla nes using X-ray absorption near-edge structure spectroscopy with synchrotro n radiation in the (Bi2-xPbx)Sr2CaCu2Oy (0 less than or equal to x less tha n or equal to 0.3) series of high-T-c superconductors synthesized by solid- state reaction in air is presented. Pb is found to have the valence of +2 i n the samples of this series. Moreover, the hole concentration increases wi th increasing Pb content. The results lead us to conclude that the substitu tion of Pb2+ in the Bi3+ sites of the (Bi,Pb)-2212 system causes the compou nds to be in the over-doped state. This effect results in the compounds hav ing a high critical current density. (C) 2001 Elsevier Science B.V. All rig hts reserved.