Substitution effects in Bi2Sr2(Ca1-xYx)Cu2O8+delta studied by X-ray absorption spectroscopy

The Bi2Sr2(Ca1-xYx)Cu2O8+delta system over the homogeneity range x = 0 simi lar to 1.0 has a maximal superconducting transition temperature (T-c) of ar ound 92 K at x = 0.2. The hole distribution of overdoped, optimum doped and underdoped states in Bi2Sr2(Ca1-xYx)Cu2O8+delta has been investigated by h igh-resolution O Kedge X-ray-absorption near-edge-structure (XANES) spectra . Near the O 1s edge, a well-pronounced pre-edge peak with maximum at simil ar to 528.3 eV is found, which is ascribed to the excitations of O 1s elect ron to O 2p hole states located in the CuO2 planes. The intensity of this p re-edge peak decreases as the Y doping increases, demonstrating that the ch emical substitution of Y3+ for Ca2+ in Bi2Sr2(Ca(1-)xY(x))C2O8+delta gives rise to a decrease in hole concentrations within the CuO2 planes. Moreover, the correlation between T-c and critical current density (J(c)) as a funct ion of doping concentration has been studied. It is important to point out that the highest J(c) across the system is appeared at the overdoped side w ith x = 0 in Bi2Sr2(Ca(1-x)Yx)Cu2O8+delta.