[en] The Ag-sheathed YBa₂Cu₃O_x high-T_c superconducting tape wires were fabricated by the powder-in-tube and rolling techniques. Annealing temperature dependence of transport critical current density J_c at 77K was studied. The optimal annealing temperature of the Ag-doped YBa₂Cu₃O_x tape wires was 910C. Transport J_c reached 1,200 A/cm² in a single filament tape wire and 1,720 A/cm² in a multifilament tape wire at 77K. It was found that the transport J_c was also dependent on the tape wire thickness; the thinner the tape wire, the higher the J_c value

[en] A preferentially oriented bulk YBa₂Cu₃O_x superconductor was prepared by the liquid phase method. A continuous dc current carrying capacity exceeding 120 A with current density higher than 37 300 A/cm² at 77 K has been obtained. The high current effects causing fracture of the sample were studied in relation to the thermal diffusion properties. In magnetization measurements, flux jumps were observed for currents in the sample a-b plane below the temperature of about 20 K. The jumps are more closely spaced with decreasing temperature or increasing field sweep rates