  High temperature (high-Tc) superconductors like cuprates have superior
critical current properties in magnetic fields over other superconductors.
However, superconducting wires for high-field-magnet applications are still
dominated by low-Tc Nb3Sn due probably to cost and processing issues. The
recent discovery of a second class of high-Tc materials, Fe-based
superconductors, may provide another option for high-field-magnet wires. In
particular, AEFe2As2 (AE: Alkali earth elements, AE-122) is one of the best
candidates for high-field-magnet applications because of its high upper
critical field, Hc2, moderate Hc2 anisotropy, and intermediate Tc. Here we
report on in-field transport properties of P-doped BaFe2As2 (Ba-122) thin films
grown on technical substrates (i.e., biaxially textured oxides templates on
metal tapes) by pulsed laser deposition. The P-doped Ba-122 coated conductor
sample exceeds a transport Jc of 10^5 A/cm^2 at 15 T for both major
crystallographic directions of the applied magnetic field, which is favourable
for practical applications. Our P-doped Ba-122 coated conductors show a
superior in-field Jc over MgB2 and NbTi, and a comparable level to Nb3Sn above
20 T. By analysing the E-J curves for determining Jc, a non-Ohmic linear
differential signature is observed at low field due to flux flow along the
grain boundaries. However, grain boundaries work as flux pinning centres as
demonstrated by the pinning force analysis.
