THE CORRELATED DISTRIBUTION OF THE ELEMENTS AND ITS INFLUENCE ON THE CRYSTAL-STRUCTURE PARAMETERS IN SINGLE-CRYSTAL (BI0.9PB0.1)2SR2(CA0.9Y0.1)CU2OZ

Single crystals of the 2212 system with the composition (Bi0.9Pb0.1)2S r2(Ca0.9Y0.1)Cu2Oz have been examined with x-ray diffractometry and sc anning electron microscopy. A correlation was found in the distributio n of Bi, Pb, Ca and Y along the sample. When part of the crystal conta ined a large amount of Ca compared with another part, then the first p art was found to be rich in Bi and relatively poor in Pb and Y. Such a correlation can be attributed to the conservation of the combined cha rge 5+ of the corresponding ions: Ca2+ + Bi3+ and Y3+ + Pb2+. The x-ra y diffraction data coincide with SEM results. They reveal that the inh omogeneity of the element distribution leads to a difference in the c parameter of the unit cell in the related parts of the crystal. These results clearly indicate the importance of determining phase purity an d homogeneity in these multicomponent, high-temperature superconductin g cuprate formulations.