Epitaxial oxidation of Ni–V biaxially textured tapes

• Published in: Physica. C, Superconductivity Vol. 377; no. 1; pp. 135 - 145
• Main Authors: Petrisor, T, Boffa, V, Celentano, G, Ciontea, L, Fabbri, F, Galluzzi, V, Gambardella, U, Mancini, A, Rufoloni, A, Varesi, E
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2002
• Subjects: Buffer layer; Coated conductors; NiO; Ni–V alloy; Buffer layer; Ni–V alloy; Coated conductors; NiO
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/S0921-4534(01)01128-5

The epitaxial oxidation of the (0 0 1)[1 0 0] textured Ni 100− x V x tapes was studied because of the practical interest of NiO as a first buffer layer for the YBCO based coated conductors. The study revealed that the oxidation of the Ni–V alloy is rather complex, the less noble V being internally oxidized, while Ni undergoes an external oxidation. Moreover, the formation of the NiVO 3 and of Ni 7V 5O 17 compounds have negative effects on the epitaxial oxidation and on the surface morphology, as well. The role of vanadium on the epitaxial oxidation of Ni–V alloy has not been fully understood yet. The optimum conditions for the epitaxial oxidation have been found to be: 700<T<800 ° C, t<30 min and P O 2 <30 mTorr. The epitaxial NiO films obtained under these conditions have a good out-of-plane and in-plane orientation, with a full-width-half-maximum of about 6.5° and 9.5°, respectively. The in-plane epitaxial relationship is [1 0 0]NiO∥[1 1 0]Ni–V. The as-obtained films have a compact and crack-free morphology, with grain sizes ranging from 30 to 300 nm. Nevertheless, the NiO films grown on (1 1 3) oriented grains or on twins are polycrystalline with a bright aspect, exhibiting a spongeous morphology. Epitaxial YBCO/CeO 2/NiO/Ni–V structures grown on the NiO template have a critical current density of about 0.6 MA/cm 2 at 77 K and zero magnetic field.