Growth of large Bi2Sr2CaCu2Oy single crystals by a vertical Bridgman method

We prepared Bi2Sr2CaCu2Oy (Bi-2212) single crystals by the vertical Bridgman method. The amount of the starting material was varied and alumina crucibles of different bottom angles were used. We found that the area of plate-like single crystals was proportional to the amount of starting materials and that the optimum bottom angle of the crucible for obtaining large single crystals was about 60 degrees. Optimizing the growth conditions leads to plate-like single crystals with sizes up to 25 x 5 mm(2) which have a zero-resistance temperature of about 80 K and a Bi-2212 single phase. Furthermore, the transition temperature width of an as-grown single crystal decreases to about 3 K by annealing at 500 degrees C for 106 h in flowing oxygen. (C) 2000 Elsevier Science B.V. All rights reserved.