A new domain structure in YBa 2Cu 3O 7− x prepared by the quench and melt growth (QMG) process

Abstract

Crystallographic analyses have revealed a new “domain structure” in YBa 2Cu 3O 7− x (123) prepared by the quench and melt growth (QMG) process. The analyses were carried out by X-ray diffractometry: a kind of pole figure method and an improved technique of microarea X-ray diffraction. The “domain structure” is composed of crystallographic units which are aligned in two-dimensions; the c-axes of them are parallel to each other and there is a slight deviation in directions of their a-and b-axes. The degree of deviation of them differs in scale: macrograins (∼ 10 mm), subgrains (∼ mm) and crystallites (∼ 100 μm) and it is about a few degrees in scale of crystallites. The “domain structure” in QMG-processed materials is closely related to their high J c values, J c > 10 4 A/cm 2 at 77 K under a magnetic field of 1 T. Crystallographic units in the “domain structure” are more strongly linked in superconducting than those in conventionally sintered specimens. The control of the “domain structure” is one of the most important factors for improving properties of superconductors.