A modified airtight two-crucible method for growth of Bi-2212 whiskers from glassy pellets

Bi2Sr2CaCu2Ox, whiskers have been grown by a modified airtight two-crucible method, employing radial and vertical thermal gradients resulting from the relative position of the crucibles. A heating profile with a constant heating rate applied from 842 to 846degreesC allows formation of whiskers up to 2 cm in length for a certain level of Al impurity in the glass. A cation-rich atmosphere is found to be a key intrinsic parameter. Our data confirm the importance of the thermal gradients, but this parameter is a somewhat extrinsic one and from a practical point of view should be correlated to other intrinsic parameters that influence growth atmosphere (i.e. to total and partial pressures). As-grown whiskers have composition Bi:Sr:Ca:Cu = (2.9-3.5):2:(1.7-2.05):(2.4-3.0) (normalized to SrA zero-resistance critical temperature T-c(R=0) = 76-98 K and maximum transport critical current density above J(c) = 10(4) A cm(-2) at 77 K in self-field.