Control of hole distribution and superconducting properties in Bi2Sr2(Ca1-xYx)Cu2O8+delta

The dependence of H-irr on the concentration and distribution of holes in t he Bi2Sr2(Ca1-xYx)Cu2O8+delta (Bi-2212) system was investigated. Coulometri c Cu(I)/(II) and Fe(II)/(III) titrations were applied to determine oxygen c ontents and distinct Cu and Bi valences and to thereby estimate the hole di stribution among the SrO-Bi2O2+deltaSrO and (Ca1-xYx)Cu2O4 blocks. With inc reasing Y-substitution level, x, continuous increase in the oxygen content and decrease in the thickness of the SrO-Bi2O2+deltaSrO "blocking" block we re observed. The extra oxygen taken in the structure only partially counter acts the trivalent-Y to divalent-Ca substitution, and consequently the hole concentration in both blocks was found to decrease. With increasing x and delta, H-irr was not enhanced but rather depressed. This suggests that the thickness of the blocking block is not the primary parameter in determining the H-irr.