Promotion of phase transformation and single-phase formation in silver-doped Tl-Ba-Ca-Cu-O superconducting thin films

Phase transformation and physical characteristics of the spray-pyrolyzed Tl -Ba-Ca-Cu-O superconducting films with 3 mol% silver dopant have been studi ed using electrical resistivity, x-ray diffraction, and scanning electron m icroscopy. The major phase formed in the resultant film, annealed at a temp erature of 885 degrees C for 3 min, was found to be the nearly single-phase , high-T-c, Tl2Ba2Ca2Cu3Oy (Tl-2223), The multiple phase of Tl2Ba2Ca2Cu3Oy and TlBa2Ca2Cu3Oy (Tl-1223) appeared at annealing temperatures lower and hi gher than 885 degrees C. It was also observed that Ag dopant effectively re duces normal resistivity at 300 K and enhances the phase transformation of single-rrl-layer Tl-1223 to double-Tl-layer Tl-2223 phases and further help s to form the nearly single-phase Tl-2223 within a short duration. Critical transition temperature (T-c,T-zero) and current density (J(c), 77 K, 0 Tes la) of the best resultant film were shown to be 123 K and 5.7 X 10(4) A/cm( 2), respectively.