GROWTH OF DOPED AND UNDOPED BSCCO-2212 CRYSTALS IN PLATINUM CRUCIBLESBY REPEATED REMELTING AND RECRYSTALLIZATION

We describe the growth of Y-doped and undoped Bi2Sr2CaCu2Oy recrystall isation technique in platinum crucibles. The conditions for the growth of high-quality, chemically pure (undoped) and highly Y-doped crystal s in platinum crucibles have been optimised. The as-grown, undoped cry stals indicate a very high T-c (onset) between 92-95 K and the Y-doped ones between 90 and 92 K with transition widths (10-90% level) betwee n 4 and 10 K. It appears that, in the case of doped batches, the cryst als with a high level of Y-doping are produced homogeneously and repro ducibly by this method, but the low-level doping produces inhomogeneou s distribution of Y within the crystal layers. The reasons are discuss ed.