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Bernhard Wörz
Wachstum biaxial texturierter NiO-Schichten auf chem. behandelten Ni5W-RABiTS und gepulste Laserdeposition epitaktischer Schichten für die Herstellung supraleitender YBa2Cu3O7-Bänder
Betreuer: Prof. Dr. Bernd Stritzker [Experimentalphysik IV]
Datum der mündlichen Prüfung: 17.02.2004
130 Seiten, deutsch , ISBN 3-89820-690-4
For the deposition of YBa2Cu3O7 (YBCO) on metallic substrates like Ni-based rolling assisted biaxially textured substrates (RABiTS), buffer layers (e.g. NiO, CeO2, Y-stab. ZrO2) are necessary. In the beginning of the deposition process of oxide layers often the formation of misoriented NiO (especially NiO(111)) is observed. It has been shown, that by Surface Oxidation Epitaxy (SOE) a biaxially textured, (001)-oriented NiO buffer layer can be grown at high temperatures (>1000 deg C) on many Ni-based RABiTS including micro-alloyed Ni, NiCr or NiV. RABiTS with high W content show very good mechanical properties but reveal some problems using the SOE method for producing a NiO buffer layer suitable for YBCO coated superconducting tapes. We explored a chemical pretreatment which makes it possible to grow (001)-oriented, biaxially textured NiO buffer layers on Ni with high (5 per cent) W content at temperatures ranging from 320 deg C to 1300 deg C and at ambient air. In this work the influence of the chemical pretreatment, the oxidation time and the oxidation temperature on the properties of self oxidized NiO layers as well as the influence of the oxidation process on the substrate properties is reported. By the deposition of a subsequent La0.7Ca0.3MnO3 buffer layer, YBCO could be grown epitaxially on Ni5W-RABiTS with first results showing a critical current density Jc of 10^5 A/cm2 and a critical temperature Tc of 89 K.