In-plane aligned superconducting Tl_(0.78)Bi_(0.22)Sr_(1.6)Ba_(0.4)Ca_2Cu_3O_9 films on rolling assisted biaxially textured substrates

摘要

In-plane aligned superconducting Tl_(0.78)Bi_(0.22)Sr_(1.6)Ba_(0.4)Ca_2Cu_3O_9 films on Rolling Assisted Biaxially Textured Substrates (RABiTS) with J_c of 4.25 X 10~5 A/cm~2 at 77 K and zero-field have been synthesized by later ablation and post-ablation annealing. The as-ablated films were amorphous due to the low substrate temperature during ablation. The amorphous films were then wrapped together with an unfired Tl_(0.95)Bi_(0.22)Sr_(1.6)Ba_(0.4)Ca_2Cu_3O_9 pellet in silver foil. The whole package was finally annealed in a tube furnace at 780-810 deg C for 40-60 min in flowing argon to crystallize the films. X-ray diffraction (XRD) shows that the annealed films consist of mainly c-axis aligned (Tl, Bi)-1223 phase with a small amount of (Tl, Bi)-1212 phase. The full width at half maximum (FWHW) values of XRD peaks show that both phases are epitaxial, with in-phase and out-of-plane alignments comparable to those of the underlying Ni and buffer layers (CeO_2 and YSZ).Four-probe transport measurements showed superconducting transition temperatures (T_cs) of 105-109 K depending on the annealing conditions. With external magnetic field applied parallel to the c-axis, irreversibility magnetic fields reached beyond 3 T at 77 K and beyond 5 T at 64 K.