We report on the transport and magnetization properties of MgB2 wires fabricated by a powder-in-tube (PIT) technique. Temperature and magnetic-field-dependent resistivity displays a high conductivity and upper critical field Hc2 generally observed in dense samples. The electronic mass anisotropy γ≈1.3±0.15 predicts some texturing in the wire. Our data on transition temperature TC, Hc2, and both magnetic and transport critical current density Jc indicate that MgB2 can be manufactured in a wire form using a PIT technique and required engineering Jc can be achieved on further optimization.
We fabricated highly textured Y1−xHoxBa2Cu3Oy (x=0, 0.2, 0.4, and 0.6) bulk samples by a ‘‘powder melting process’’ method under identical conditions and investigated their critical current densities and flux pinning behavior with a superconducting quantum interference device magnetometer. The dependence of Jc on the magnetic field, estimated by the Bean model, is studied. The results indicate that Jc drops with the magnetic field according to a power law Jc∝H−n (n<0.5), which implies that the Jc value of these samples is controlled by the flux pinning rather weak links. It is found that Jc and flux pinning can be significantly improved by Ho substitution for Y in Y-based superconductors. The reduction of the size of Y2BaCuO5 particles, stress-field pinning, and magnetic pinning created by the Ho addition are considered to be responsible for the increase in Jc and flux pinning.
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