TEXTURE DEVELOPMENT OF HTS POWDER-IN-TUBE CONDUCTORS

An overview of the fabrication and electromagnetic properties of high- temperature conductors processed by the powder-in-tube (PIT) technique with reference to texture development and critical anisotropy data is presented. Special emphasis is given to the optimization of the physi cochemical and electromagnetic parameters of the multifilamentary and single-filament conductors with superconducting cores of Bi-2223, Tl-1 223 and Y-123 superconducting phases. The influence of the multifilame ntary and single-filament structures on texture development is discuss ed. Also, the importance of the local disturbances of the grain alignm ent and microdefects for the current distribution across and in the pl ane of the whole conductor is analysed. A comparative study of the cri tical current anisotropy with field direction in low magnetic fields o f Tl-1223 and Bi-2223 conductors manufactured by the PIT technique is presented. For Tl-1223 PIT conductors the anisotropy coefficient shows a very pronounced minimum, followed by a monotonic reduction of aniso tropy with the increase of the magnetic field. This is explained in te rms of poor grain alignment with weak intergranular superconducting co upling which cause 3D current percolation and also by the demagnetizin g effect of the grains and the ceramic core in the PIT Tl-1223 tapes.