PB SUBSTITUTION IN THE BI2SR2CACU2O8-T-C SUPERCONDUCTOR - CATION OVERDOPING(DELTA HIGH)

We study the effects of Pb substitution in single crystals of the high -temperature superconductor Bi2Sr2CaCu2O8+delta. We compare Pb-substit uted samples with ''pure'' (unsubstituted) crystals in terms of struct ure, cation composition, and the temperature dependences of ac suscept ibility and Raman scattering. We find that Pb2+ primarily substitutes for Bi3+, leading directly to a T-c, reduction characteristic of overd oped samples. We also observe structural changes related to the superl attice modulation along b. Raman scattering studies indicate that som e Pb atoms go to Sr sites. Low-temperature electronic Raman scattering shows further evidence for cation overdoping by comparison with oxyge n annealed pure Bi2Sr2CaCu2O8+delta.