Abstract
A main challenge that significantly impedes REBa2Cu3Ox (RE = rare earth) coated conductor applications is the low engineering critical current density Je because of the low superconductor fill factor in a complicated layered structure that is crucial for REBa2Cu3Ox to carry supercurrent. Recently, we have successfully achieved engineering critical current density beyond 2.0 kA/mm2 at 4.2 K and 16 T, by growing thick REBa2Cu3Ox layer, from ∼1.0 μm up to ∼3.2 μm, as well as controlling the pinning microstructure. Such high engineering critical current density, the highest value ever observed so far, establishes the essential role of REBa2Cu3Ox coated conductors for very high field magnet applications. We attribute such excellent performance to the dense c-axis self-assembled BaZrO3 nanorods, the elimination of large misoriented grains, and the suppression of big second phase particles in this ~3.2 μm thick REBa2Cu3Ox film.
Highlights
MethodsThe ~3.2 μm thick REBCO film was grown on a ~12 mm wide, ~50 μm thick standard buffered IBAD Hastelloy substrate using standard tetramethyl heptanedionate precursor by multi-pass MOCVD deposition[43]
We have demonstrated that, using a multi-pass MOCVD process, high Je is feasible in thick Zr-added REBCO films above 3 μm
Such a high Je has been possible through the elimination of large misoriented grains and suppression of big second-phase particles, as well as the growth of high density of c-axis self-assembled BZO nanorods
Summary
The ~3.2 μm thick REBCO film was grown on a ~12 mm wide, ~50 μm thick standard buffered IBAD Hastelloy substrate using standard tetramethyl heptanedionate precursor by multi-pass MOCVD deposition[43]. Under the heater temperature of 960 °C, the tape was coated with a ∼1.1 μm thick REBCO film in the first pass, cooled down to room temperature, and was coated with the second ∼1.1 μm thick film on the first layer in the second pass, and subsequently the third layer. A ∼2 μm thick silver layer was deposited on the REBCO film as a protection and current contact layer. To introduce c-axis aligned BZO nanorods, 20 mol% Zr tetramethyl heptanedionate (thd) was added into the standard precursor solution with a nominal cation composition of (Gd0.6Y0.6)Ba2.15Cu2.15. The growth condition and the precursor are same for each pass
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