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Texture formation of the partially melted process of solution-spun Y1Ba2Cu3Ox, was examined to enhance the reproducibility of the high Jc of the filament. The effect of Rh addition on the texture formation was also investigated. Controlling the cooling rate through peritectic temperature to produce 123 is the key for obtaining the reproducible high Jc. A well-aligned texture in the present filament needs a relatively high cooling rate for the following 123 crystal growth, such as 40 °C/h. Addition of Rh promotes the preparation of the 123 phase and enhances the Jc.

The filaments have been prepared by dry spinning through a homogeneous aqueous solution containing mixed acetates of Y, Ba, and Cu, polyvinyl alcohol, and organic acids. After spinning, the filament was sintered or partially melted to generate the superconducting phase. Magnetization properties of the filaments are examined. Since solution spinning introduces a fine flux pinning center into the superconducting phase, such as at elemental level, a significantly improved Jc value estimated from the magnetization curves and field dependence of the Jc have been achieved in the solution-spun filament. The phase decomposition from the 124 phase to the 123 phase and partial melting result in an enhancement of flux pinning.

A high Tc superconducting (Bi, Pb)–Sr–Ca–Cu–O filament was prepared using a combined technique of suspension spinning and densification of the pyrolyzed filaments by pressing and sintering. The effects of the Jc of the filament obtained on the spinning and densifying conditions were examined. The Jc was dependent on the composition of the starting powder and the kind of suspension medium. The Jc was strongly affected by the pyrolyzed condition and densification time. The highest Jc value at 77 K, 0 T of 1900 A/cm2 was attained for the filament sintered under the optimum sintering condition. The grains in the filament were oriented with the c axis perpendicular to the filament surface, and the coupling of the grains in the perpendicular to the filament surface was weaker than that for the parallel direction in the filament surface.

High Tc Tl–Ba–Ca–Cu–O (A) and Tl–Ba–Sr–Ca–Cu–O (B) superconducting filaments were successfully prepared using a technique in which suspension spun and pyrolyzed filaments were densified by pressing and sintering. A zero resistance state was achieved at 112 K and 106 K, and the maximum Jc at 77 K, 0 T was 1200 A/cm2 and 2300 A/cm2 for Tl–Ba–Ca–Cu–O (A) and Tl–Ba–Sr–Ca–Cu–O (B) filaments, respectively. Although the starting powder had a high Tc phase of Tl2Ba2Ca2Cu3Ox, the structure of the filament with high Jc was a high Tc phase of Tl1Ba2Ca2Cu3Ox, due to the volatility of Tl oxide from the large surface area of the filament.

The suspension spinning of a Ba2Y1Cu3Ox superconductor under various conditions was studied to prepare a long filament with high Jc. The oxide powder was suspended in a PVA solution containing a dispersant. The viscous suspension was extruded as a filament into a precipitating medium and coiled on a winding drum. The obtained filament was heated to remove volatile components and to generate the layered perovskite phase. The spinning was examined in an aqueous system and a nonaqueous system. The filament with higher Jc was obtained for the nonaqueous solution. The Jc was dependent on the fineness of the starting oxide powder, solvent, precipitating medium, degree of polymerization of PVA, the kind of dispersant used, and the oxide powder contents of the spinning dope, as well as the heating condition. The highest Jc value obtained by resistivity measurement at 77 K and zero field, 680 A/cm2, was attained for the filament spun under optimum spinning conditions. The magnetization curve of the filament showed that the material was a type II superconductor. The hysteresis of thin filaments was relatively small compared with that for the thick filaments. The Jc at 79 K, estimated from the magnetization curve, was one order of magnitude higher than the Jc measured by the resistivity method and decreased drastically with increasing field.