Texturing of Micaceous Superconductor Powder and Fabrication of Wire to Preserve the Texture

Fabrication and characterization of green-state Bi-2212 ribbons

“…To achieve a round wire based upon the textured ribbons fabricated using the Chilsonator, a modified jelly-roll conductor has been outlined [4] and follows closely the classical work of McDonald [10]. Such a conductor will take full advantage of the texture imparted by the roll processing method, while connectivity and densification will be achieved by the non-melt heat treatment reported elsewhere [5].…”

“…developed in a previous work [4] and defined in Equation 1, was calculated from the x-ray data to provide a quantitative, comparative measure of sample texture. This texture parameter has a value of 0 for randomly oriented samples and a value of 1 for a single crystal spectrum taken along the c-axis.…”

“…In previous work, uniaxial mechanical pressures as low as 140 MPa applied to randomly oriented fine powders in a simple die set resulted in dense, highly textured pellets. The current work builds upon this premise by developing the technology to create continuous lengths of high density, strongly textured Bi-2212 ribbons, which may be processed through a 'jelly-roll' method to form multifilament round wire [4].…”

Studies of porosity, connectivity, and parasitic phases in textured Bi-2212/Ag after non-melt heat treatments

“…The texture is measured using X-ray diffraction (XRD, Bruker D8-Focus), shown in FIGURE 1c, in which the amplitudes of the (00l) diffraction lines produced when the c-axis is normal to the plane of the sample are compared with the amplitudes of (11l) lines which are the strongest in the completely random powder. A texture parameter W was defined in a previous paper [2] which yields the value 0 for random grain orientations and 1 for full texturing where all grains have their ab planes parallel to the sample face. For the green-state samples analyzed in this work, we obtained W = 0.13 for the un-compacted powder, W = 0.32 for green-state cores in conventionally processed OPIT wire (Oxford Superconducting Technology), and W = 0.68 for the sample shown in FIGURE 1.…”

“…The method begins with a procedure by which a continuous ribbon of highly textured Bi-2212 fine powder on a silver foil substrate was formed. This procedure has been discussed in a previous paper [2] and has now been successfully implemented as reported in another paper at this conference [3]. It continues with a procedure by which the textured layer was formed into a 'jelly-roll' round billet which will be extruded and drawn to fine-wire dimensions.…”