Effect of Wire Diameter on the Microstructure and $J_{{\text{c}}}$ Properties of Ba_0.6K_0.4Fe₂As₂ Tapes

For Ba _0.6 K _0.4 Fe ₂ As ₂ (Ba-122) superconducting tapes, which are made of round wires by a flat rolling process, the final diameters of the wires are critical parameters for the transport critical current density (J _c ). X-ray diffraction and scanning electron microscopy analysis revealed that the degree of texture is stronger in the samples rolled from wires with larger diameters. The hardness test showed that the highest density is obtained in the tapes rolled from wires of 1.8 mm in diameter in which the highest J _c of 3.31 × 10 ⁴ A · cm ^-2 at 4.2 K and 10 T was achieved. It is suggested that superior J _c performance can be obtained in the samples with both large texture degree and high core density. Enhancing the texture and density is one way if we want to make small sized tapes with high transport J _c .