Joerg Eickemeyer

Reel-to-reel MOCVD for YBCO coated conductor

A reel-to reel MOCVD system has been developed for a fast and economic process to get high quality YBCO coated conductor tapes. Several oxides buffer layer sequences (based on YSZ, CeO/sub 2/, Y/sub 2/O/sub 3/...) were then grown epitaxially on two kinds of tape. Effective stacking for MOCVD reported here are YSZ/Y/sub 2/O/sub 3//YBCO and YSZ/CeO/sub 2//YBCO, respectively, on oxidized Ni RABiTS microalloys (0,1% W) and on SS/YSZ (IBAD) tapes. First, EBSD and AFM techniques have been used to characterize the substrates. Superconducting YBCO films were fully characterized by SEM, XRD and AC susceptibility measurements Epitaxial growth was depicted with a strong in-plane and out-of plane texture: FWHM of YBCO /spl phi/-scans were 8.5/spl deg/ on Ni tape and 9/spl deg/ on IBAD Hastelloy tapes. High performances were also measured by AC susceptibility, with J/sub c/ values of 0.6 MA/cm/sup 2/ at 77 K (0 T) on Ni tape and close to 1 MA/cm/sup 2/ on IBAD substrates, with a sharp transition (/spl Delta/T/sub c/ < 0.4 K) and a T/sub c/ onset at 90 K. Deposition of 2 meter buffered YSZ and CeO/sub 2//YBCO films have also been performed showing good in-plane alignment (/spl phi/-scan YSZ: FWHM = 11/spl deg/) with a tape velocity set at 4 m/h.

YBCO films on buffered Ni RABiT substrates by pulsed injection MOCVD

Abstract Biaxially textured buffer layers and YBa 2 Cu 3 O 7 (YBCO) films were grown on NiO/Ni based substrates by pulsed injection MOCVD. High quality biaxially textured NiO layers have been prepared following an optimised recrystallisation–oxidation process. The yttria stabilized zirconia (YSZ) and its combination with CeO 2 and/or Y 2 O 3 were investigated in the role of buffer layers for YBCO. Thin biaxially textured buffer layers were deposited in a temperature range from 600 to 800 °C. The best superconducting properties correspond to the Ni/NiO/YSZ/Y 2 O 3 /YBCO architecture: YBCO layers were grown epitaxially and exhibited a critical temperature T c ∼90 K ( ΔT c ⩽1 K) and critical current densities J c ⩾5×10 5 A/cm 2 at 77 K.

YBaCuO deposition by MOCVD on metallic substrates: a comparative study on buffer layers

YBaCuO films of about 1 /spl mu/m thickness have been deposited by metal organic chemical vapor deposition (MOCVD) on biaxially textured Ni-based substrates. Different buffer layers (MgO, YSZ, CeO/sub 2/), and also NiO epitaxially grown on Ni, have been tested with subsequent YBCO deposition in the same reactor. When using NiO as first buffer layer, Ni-based substrates were oxidized in a rapid thermal processing system or in a conventional furnace previous to deposition of the second buffer layer. In the present work, we study different conductor architectures from the point of view of T/sub c/, J/sub c/ (77K), epitaxial growth, and chemical stability of the structure.