Single crystal growth and structural analysis of La/sub 6. 5/Sr/sub 1. 5/Cu/sub 8/O/sub 20/

The discovery of high-T/sub c/ superconductivity has promoted several studies regarding the stability range of different possible stable phases in copper oxide compounds. In particular, in the La/Cu/M/O (M: Sr, Ba) system, a number of stable compounds have been reported. The latter solid solution was the only one to become superconductor near 40 K (in the range chi = 0.2). Although many physical properties of this phase were elucidated through studies on ceramic powder samples (pellets), many other unavoidably required the use of single crystals (the search of anisotropic effects assignable to the Cu-O layers as origin of a layered superconductor character). The aim of the present work is to investigate the character of phase II (composition analysis, structural properties) and their possible relationship to other stable phases found in the literature. The crystals were characterized by Scanning Electron Microscopy (SEM), X-Ray Diffraction, Electron Probe Microanalysis (EPMA), and SQUID, for susceptibility measurements.