Correlation between vortice state and texture of YBa2Cu3O7-x ceramics

E.M. Ibragimova1, M.U. Kalanov1 and M.A. Kirk2

1 Institute of Nuclear Physics, Tashkent, Uzbekistan;
2 Argonne National Laboratory, Argonne, Illinois, USA

Two ways are known to increase the critical current density jc of superconducting materials: 1) to generate strong pinning centers by a proper irradiation and 2) to form anisotropic texture minimizing weak intergranular contacts.  The both approaches were combined in this work to study the effect of texturing degree and structure defects of YBa2Cu3O7-x ceramics on magnetization and transport critical current densities.
Samples of 12 mm diameter and 1 mm thick were sintered in the 60Co gamma-ray field of 20-2000 R/s at 900-950 C and had the following parameters: a=3.824, b=3.885, c=11.878 , oxygen index x=0.07, critical temperature Tc 91-92 K, texturing degree Ft = 0.5-0.8, density 5.5 g/cm3. Reference isotropic (Ft=0) sample sintered by the standard powder technology had a low value of density 4.9 and jc~50 A/cm2 at 77 K, but a high magnetization at strong (0.5-5 Tesla) magnetic fields at 10 K. Several samples with Ft=0.5-0.6 contained 5-6 % non-conducting impurity phases, showed a higher magnetization in weak (<160 Oe) and the strong fields at 10 and 77 K, although a higher transport jc ~100 A/cm2 at 77 K. Single phase highly textured (Ft= 0.7-0.8) samples exhibited the maximal value of jc~ 1000 A/cm2 at 77 K, although a bit weaker magnetization than the multiphase samples. The obtained results show, that the transport critical current density depends directly on the texturing degree, magnetization in strong fields at 10 K depends on granularity, and that at 77 K - on the texture degree. Thus, it seems possible to find such a thermoradiation treatment, when both magnetization and transport critical current would increase.