MICROSTRUCTURE OF BI2212 AND (BI PB)2212 SINGLE-CRYSTALS AND EFFECT OF ELECTRON-DONORS AND ACCEPTORS/

Pure and lead doped Bi2Sr2CaCu2O8 (Bi2212) single crystals were grown an their structures were studied by several methods, especially by res istivity measurements, electron microprobe and Raman micro-spectroscop y. The microstructure and the Raman spectrum of Bi2212 were analyzed i n comparison to those of Bi2201 and Bi2223 single crystals. In these s tructures, the existence of close, staggered and antiparallel Bi-O bon ds leads to a Raman doublet al 653 and 627 cm-1 which corresponds to c oupled motions in these bonds. The intercalation of iodine in Bi2212 s uppresses this staggered configuration and gives a more homogeneous ve rtically aligned distribution of (Bi)O(Cu) bonds. In these intercalati ons, the presence of unsymmetrical I3- ion is demonstrated. Similar bo nd-ordering was observed on intercalation with chloranil and tetrahydr ofuran. By lead doping, the staggered bonds are no longer identical an d the decoupling leads to a single phonon around 623 cm-1 and confirms that Pb occupies Bi position.