Practical superconductor development for electrical power applications : annual report for FY 2001. Page: 34 of 88
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YBCO on IBAD-YSZ Substrates
Biaxially aligned YBCO films were deposited on IBAD-YSZ-buffered HC
substrates by PLD under the conditions listed in Table 5. An XRD 20-scan of
YBCO directly deposited on HC substrate reveals tiny YBCO (100) peaks, as
shown in Fig. 30a. Before PLD of YBCO, a CeO2 buffer layer (thickness ~10 nm)
was deposited on the YSZ by e-beam evaporation to reduce the lattice mismatch
between YBCO and YSZ. Deposition of the ceria buffer layer on the YSZ film
helped to reduce a-axis misalignment and improve c-axis alignment, as shown in
Fig. 30b. The YBCO (100) peaks disappeared in the XRD pattern of the sample
with the ceria buffer layer. Layer-by-layer XRD 4-scans of the sample indicated
epitaxial growth of the CeO2 and YBCO films, as shown in Fig. 31. In-plane-
texture FWHMs of 120 and 90 were observed for CeO2 (111) and YBCO (103),
respectively.
Table 5. Conditions used for PLD of YBCO on IBAD-YSZLaser wavelength 248 nm (Kr-F)
Repetition rate 8 Hz
Pulse width 25 ns
Energy density 1-3 J/cm2
Substrate temperature 700-800 C
Operating pressure 100-300 mtorr
Oxygen flow rate 10 sccm
Target-to-substrate distance 4-8 cmA YBCO film (0.5- m thick) was deposited by PLD on ceria-buffered IBAD-
YSZ that was fabricated on HC substrate. Inductive measurements (Fig. 32)
showed that Tc (onset) = 90 K and the superconducting transition was completed
at 88.5 K. Jc(transport) for this sample was 2.2 x 106 A/cm2 at 77 K with zero
external field.
2.1.3 YBCO Films from a Solution Process
Various processing methods are being investigated for the fabrication of
YBCO-coated conductors on metallic substrates. Promising options include
nonvacuum ex-situ processes such as metal organic deposition (MOD) and sol-
gel processing. Solution techniques are now being studied by several groups,
and some of their results are comparable to superconducting performance levels
obtained by vacuum processes such as PLD. Of the solution techniques, the26
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Cha, Y. S.; Dorris, S. E.; Dusek, J. T.; Emerson, J. E.; Erck, R. A.; Fisher, B. L. et al. Practical superconductor development for electrical power applications : annual report for FY 2001., report, May 2, 2002; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc737902/m1/34/: accessed July 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.