QUANTITATIVE-ANALYSIS OF GRAIN ALIGNMENT IN CERAMIC BI-2223 SUPERCONDUCTOR POWDER BY PRESSURE-ASSISTED COMPRESSION

The alignment of grains in isostatically pre-compacted samples of (Bi, Pb)(2)Sr2Ca2Cu3O10+delta high-T-c superconductor has been achieved by pressure-assisted compression (PAC) at room temperature. Hydrostatic p ressures ranging from 200 to 800 MPa were intended to confer ductility to this polycrystalline ceramic material during its deformation while compressive stresses applied in order to promote grain alignment led to strain rates up to 50%. Using image analysis and X-ray diffraction, quantitative analyses show that, for any hydrostatic pressure, grain alignment appears at strain rates above 10% and becomes very pronounce d at strain rates around 50%. Further improvement of the PAC technique with compressive stresses applied cyclically even led to a very dense sample with a global disorientation angle between grains equal to 5 d egrees and a transport critical-current density after sintering of 10( 7) A/m(2) at 77 K and zero applied field. (C) 1997 Elsevier Science B. V.