GROWTH OF BSCCO 2212 CRYSTALS IN FLAT DISH-SHAPED CRUCIBLES

We report the growth of undoped and Y- and Gd-doped Bi2Sr2CaCu2O8 (BSC CO 2212) crystals by the flux method in flat dish-shaped crucibles whe re the growth mechanism appears to be different from that observed in standard high form or conical crucibles. The crystals exhibited two di fferent morphologies with two different properties. Thin plate crystal s grew at the surface of the melt (type 'A'), and others grew under th e top layer as polygonal thick blocks (type 'B'). The orientation and the habit of the 'A' crystals were dependent on the growth conditions, they were free from any detectable Al contamination or flux inclusion s and were good quality 2212 crystals exhibiting high as-grown T-c (on set) between 90 and 93 K with transition widths between 2 and 10 K. On the other hand, the polygonal blocks were mixed with flux and indicat ed a T-c (onset) of 86 K with a broader transition width. The influenc e of the shape of the crucible and the possible growth processes are d iscussed.