Dresden 2003 – wissenschaftliches Programm

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M: Metallphysik

M 32: Intermetallische Phasen II

M 32.5: Vortrag

Mittwoch, 26. März 2003, 17:30–17:45, IFW B

Chemical composition, microstructure and superconducting properties of MgB2 wires and tapes — •Dominique Eyidi, Balaji Birajdar , and Eibl Oliver — Institut fuer Angewandte Physik – Universitaet Tuebingen - Auf der Morgenstelle 10 - D-72076 Tuebingen Germany

The chemical composition, the microstructure and the superconducting properties of metal-sheathed MgB2 tapes and wires synthesized by the powder-in-tube technique were investigated. Critical current densities up to 10 000 Amperes pro square centimeter, and critical temperatures of about 39 K were evaluated by transport measurements in the MgB2 samples. Electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and analytical transmission electron microscopy (TEM) were used to study the chemical composition and the microstructure of the samples, and a special attention was given to the boron analysis. The oxygen content in the MgB2 matrix was determined by EPMA and varied from 5 to 1 atom percent. The grain size varies from 20 nm to 1 micrometer. Elemental maps of oxygen and boron in the matrix were acquired by electron spectroscopic imaging (ESI) in the TEM and yielded MgO grains about 20 - 300 nm in diameter and randomly distributed. Tape samples showed boron-rich secondary phases (MgB4, MgB7) embedded in a MgB2 matrix. The wire sample did not show any boron-rich phase.