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

Abstract

Bi2Sr2CaCu2Ox whiskers have been grown by a modified airtight two-crucible method, employingradial and vertical thermal gradients resulting from the relative position of thecrucibles. A heating profile with a constant heating rate applied from 842 to846 °C 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 theimportance of the thermal gradients, but this parameter is a somewhat extrinsic one and froma practical point of view should be correlated to other intrinsic parameters that influencegrowth atmosphere (i.e. to total and partial pressures). As-grown whiskers have compositionBi:Sr:Ca:Cu = (2.9–3.5):2:(1.7–2.05):(2.4–3.0) (normalized toSr2), zero-resistancecritical temperature Tc (R = 0) = 76–98 K and maximum transport critical current density aboveJc = 104 A cm−2 at 77 K in self-field.