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)2Sr2(Ca0.9Y0.1)Cu2Oz have been examined with X-ray diffractometry and scanning electron microscopy. A correlation was found in the distribution of Bi, Pb, Ca and Y along the sample. When part of the crystal contained a large amount of Ca compared with another part, then the first part 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 charge 5+ of the corresponding ions: Ca2++Bi3+ and Y3++Pb2+. The X-ray diffraction data coincide with SEM results. They reveal that the inhomogeneity 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 and homogeneity in these multicomponent, high-temperature superconducting cuprate formulations. (author)