Characterization of Electrospun Bi₂Sr₂CaCu₂O_8+δ Nanowires with Reduced Preparation Temperature

Bi₂Sr₂CaCu₂O_8+δ (Bi-2212) nanowires were fabricated employing electrospinning. A subsequent thermal treatment based on thermal gravity analysis is required to obtain the final crystal structure and superconductivity; however, if this preparation temperature is too high, the nanowire structure may completely collapse during the treatment, which is even more pronounced when aligning the nanowires. Therefore, Li acetate was added in various amounts to the starting composition, which enabled to produce the desired Bi-2212 phase already at about 750 °C instead of 840 °C. An X-ray and a TEM analysis proved that the resulting nanowires were single-phase Bi-2212. After the electro-spinning process, the resulting samples form fabric-like networks, and in the heat treatment, the nanowire structure was found to survive. The nanowires exhibited a polycrystalline structure with grain sizes of 20-50 nm, an average wire diameter of ∼100 nm, and a length of up to several micrometers. The resulting nanowire network samples were characterized by magnetic measurements and electric transport measurements in fields up to 9 and 4 T, respecitively.