Processing of Bi₂Sr₂CaCu₂O_x thick films from nitrate precursors

High-quality Bi₂Sr₂CaCu₂O_x/Ag superconducting tapes were fabricated directly from the nitrate salts of Bi, Sr, Ca, and Cu by the partial-melt-growth technique. Nitrate particles were deposited electrostatically on the Ag substrate and heat treated. After process optimization of the superconducting tapes, the best samples showed typical T_c of 89 K with zero applied field critical current density of 2×10⁴ A/cm² (I_c=11.2 A) at 77 K and 2.6×10⁵ A/cm² (I_c=190 A) at 4.2 K. Unlike films grown using solid state reacted precursor powders, these films lacked the typical Bi-free, needlelike defects and possessed a smooth morphology. X-ray diffraction patterns showed the film to be highly c-axis oriented. The processing of these tapes significantly reduces the overall fabrication time from precursor materials preparation to final heat treatment.