Critical current studies on metal clad R1Ba2Cu3O7−x wires

Silver clad wires of R₁Ba₂Cu₃O_7−x (R=Y, Gd, Sm, Dy and Ho) have been fabricated following the powder-in-tube method and cold-rolling. The critical current densityJ _c at 77 K and zero magnetic field is restricted to 66 A.cm⁻². In a separate experiment we have studied the effect of silver sheath thickness onJ _c of the Y₁Ba₂Cu₃O_7−x wires. Interestingly,J _c is higher for larger sheath thickness indicating that large sheath thickness prevents oxygen loss during sintering. Uniaxial pressing of the wires into flat tapes results in an increase of theJ _c . MaximumJ _x is, however, limited to 169 A.cm⁻². No grain alignment is found in the core material of our wires which is essential for highJ _c . Several options are being tried.