Development and Characterization of P-doped Ba-122 Superconducting Tapes

Abstract

Among the recently discovered Fe-based superconducting compounds, the Ba-122 phase has proved to be the more attracting for the development of powder in tube (PIT) processed conductors. In fact, after some years of development, critical current densities (<italic>J_c</italic>) of about 10⁵ A/cm² at 4.2 K and magnetic fields up to 10 T have been obtained in (Ba_0.6K_0.4)Fe₂As₂, PIT wires and tapes. To develop a safe upscaling method, the synthesis of the powders is a crucial point. In order to avoid the use of highly reactive K we have developed BaFe₂(P_1-xAs_x)₂ PIT tapes. This compound has proved to be very stable and in form of crystals and thin films exhibits excellent critical current: We succeeded in manufacturing PIT tapes with this phase with <italic>J_c</italic> values of about 10³ A/cm² at 4.2 K in self-field. Detailed microstructural and chemical investigations of the samples have been performed by high-resolution TEM, scanning TEM, and electron energy loss spectrometry analysis. A deformation network inside the grains that can induce strong pinning has been observed. However, chemical inhomogeneities at the grain boundaries are also present, which limit the transport current.