Sinter-forging of strongly textured Bi2223 discs with largeJ_cs: nucleation and growth of Bi2223 from Bi2212 crystallites

Abstract

Dense Bi2223 superconductor discs with a highly oriented structure were prepared by the sinter-forging method. A detailed investigation of the processing parameters has been carried out on the phase assemblage, the particle size of the calcined precursor powder and the sinter-forging time and temperature. A high transport critical current density, J c , was obtained from a starting powder rich in Bi2212 and secondary phases. Using fine powder, a high degree of orientation, larger than those of multifilamentary tapes, and excellent intergrain connection were observed. The optimal sinter-forging temperature was found to be in the range of 845-850• C and the transport critical current densities reached values of 12 700 A cm −2 at 77 K in self-field. The combination of textural and microstructural investigations testify that a nucleation-growth mechanism from the Bi2212 particles is responsible for the Bi2223 phase formation, rather than an intercalation process.

Quantitative texture analysis of polyphased oxides by diffraction: example of Bi2223 sinter-forged ceramic and Y123 foam superconductors

“…It should be noticed that this effect is observed for closely developed textures between the Bi2212 and Bi2223 phases which ensures enough links for the current paths in the compound. These close textures are coming from the nucleation-growth mechanisms between the two phases, which is achieved in the sinter-forging method [4]. We do not have any hint at the moment whether if achieving FWHDs smaller than 14 • [5] may still enlarge J c 's, but compared to YBCO thin film textural values [11] the ones observed in this work are 4-6 times larger.…”

“…We used experimental strategies detailed elsewhere both using neutrons [7] and X-rays [8]. The key point in our measurements is the presence of several low crystal-symmetry phases which obliges us either to restrict the measured angular range, when possible [4], or to use position sensitive detectors in order to avoid prohibited acquisition times [8]. The important input of such procedure is the availability to calculate afterwards phase ratios, orientation distribution functions (ODFs), structures, crystallite sizes and microstrains, residual stresses.…”

“…1. Comparison of transport critical current density and FWHD with sieve size [4]. and poor connectivity, which explains the weak transport critical current density of sample composed of powder obtained from a 200 m sieve.…”

“…The most appropriate method for such quantitative texture determination is the calculation of the OD from pole figure measurement [3], which we use here. For textured Bi2223 discs, it is then possible to extract the distribution of crystallites orientations around c-axis [4][5][6], and for Y123 foams using neutron experiment, the distribution of orientations in the whole volume of irregularly shaped samples.…”

Synthesis and thermoelectric properties of Bi2.5Ca2.5Co2Ox layered cobaltites

“…Since our hot-forged materials have axially symmetric fiber textures (i.e., random in-plane distribution of crystallite a and b axes), the complete texture analysis was made by measuring the inclination of the {00l} crystallographic planes in terms of the sample surface. 8,9 The Gaussian integrated (005) peak intensities were normalized into distribution densities by the direct normalization procedure 9 and used as input to reconstruct -scans, which represent the {00l} plane dispersions of the crystallites. The maximum of the distribution densities (DD max ) was extracted from the -scan Gaussian profile and used as parameter for a quantitative appreciation of the crystallite dispersion and texture strength.…”