Growth of large Bi2Sr2CaCu2Oy single crystals by a vertical Bridgman method

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