Films of BSCCO superconductors prepared by spray pyrolysis of carboxylates

Films of BiSrCaCuO (BSCCO) superconducting films with additions of PbO have been prepared by spray pyrolysis of a mixture of carboxylates on (100) MgO substrates. The thickness of the films ranged between 4 and 6 μm. The films were characterized by X-ray diffraction (XRD), electron microprobe analysis resistance versus temperature (R versus T), scanning electron microscopy (SEM), the ability to pattern the films by photolithography and microwave transmission (MWT). XRD results show a mixture of the 2212 and 2213 phases with a certain degree of preferred orientation of the (001) for the 2212 and (hkl) for the 2223 phase. R versus T shows T_c (R = 0) ranging from 84 to 100 K, with ΔT = T_onset - T_c (R = 0) varying between 2 and 10 K. SEM studies show regions with uniform coverage of single phase 2212 as well as two phase regions, which explain the difference in T. The films allow patterning by photolithography using laser ablation or ion milling with line widths down to 20 μm. However, so far the authors have been unable to pattern a microbridge and the J_c at 77 K in the best films is estimated to be larger than 10³ A cm^-2. MWT measurements were carried out when the sample was mounted across the waveguide and the ratio of transmitted to incident microwave power was measured at 9.5 GHz. The measured film has a T_c of ≈94 K and the transmission is very slightly (≈ 5%) sensitive to a magnetic field of 100 G. The MWT is not changed after three cycles of heating to room temperature.