Effect of Annealing DC-Sputtered Bi,Pb-2223 Thin Films

Thin films of Bi-2223 fabricated on SrTiO₃(100) substrates by dc sputtering were found to have a transition temperature (T_c) as low as that of bulk-phase Bi-2223. Subsequent annealing of these precursor films in the presence of Bi,Pb-2223 pellets increased this T_c value from 72 to 105 K, making it comparable to bulk-phase Bi,Pb-2223. Strong (00l) peaks and a sharp quadrupole were observed in this annealed film, indicating a main phase of Bi,Pb-2223 with a c-axis orientation by the X-ray diffractometry (XRD) measurements. A maximum critical current density (J_c) of 3.3 × 105 A/cm² at 77 K was also obtained with the Bi,Pb-2223 thin film, which is a value that is much higher than that of commercial Bi,Pb-2223 tapes. J_c values of thin films were strongly dependent on the annealing temperatures between 854 °C and 866 °C. In this temperature range, XRD data show that the thin films were not a single phase of Bi,Pb-2223, suggesting only a slight interruption of the supercurrent. Although, the films have a good c-axis and ab-axis alignments. Thus, although the films were not perfect, the improvement in microstructure allows for a much higher J_c value.