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 (J(c)) of about 10(5) A/cm(2) at 4.2 K and magnetic fields up to 10T have been obtained in (Ba0.6K0.4)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(P1-xAsx)(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 J(c) values of about 10(3) A/cm(2) 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.