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

Abstract

Phase transformation and physical characteristics of the spray-pyrolyzed Tl-Ba-Ca-Cu-O superconducting films with 3 mol% silver dopant have been studied using electrical resistivity, x-ray diffraction, and scanning electron microscopy. The major phase formed in the resultant film, annealed at a temperature 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 higher than 885 degrees C. It was also observed that Ag dopant effectively reduces 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 helps 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 Tesla) of the best resultant film were shown to be 123 K and 5.7 X 10(4) A/cm(2), respectively.