ELECTRONIC STATES AND SUPERCONDUCTING PROPERTIES OF BI2SR2(CA,GD)CU2OY STUDIED BY X-RAY PHOTOELECTRON AND INVERSE-PHOTOEMISSION SPECTROSCOPY

Measurements of superconducting properties, X-ray photoelectron and in verse-photoemission spectroscopy have been performed on Bi2Sr2Ca1-xGdx Cu2Oy (0 less than or equal to x less than or equal to 1.0) ceramics, where the metal-insulator transition is observed at x similar to 0.6, The density of states at the Fermi level is reduced with increasing Gd ion contents at Ca sites. Annealing the samples in vacuo increases th e critical temperature even at optimum hole concentration (x = 0.1). C hanges in the electronic states are discussed in terms of the hole con centration.