Non-Vacuum Deposition of Buffer Layer for YBCO Superconductor Oxide Films
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Non-Vacuum Deposition of Buffer Layer for YBCO Superconductor Oxide Films
Raghu Bhattacharya, Sovannary Phok, Priscila Spagnol, and Tapas Chaudhuri National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, USA ABSTRACT Nonvacuum electrodeposition was used to prepare biaxially textured CeO2 and Sm-doped CeO2 coatings on Ni-W substrates. The samples were characterized by X-ray diffraction (including θ/2θ, pole figures, omega scans, and phi scans), atomic force microscopy, and Auger electron spectroscopy (AES). Pole-figure scans show that electrodeposited CeO2 and Sm-doped CeO2 on textured Ni-W (3 at.%) is cube textured. Full-width at half-maximum values of the ω scan and φ scan of the electrodeposited layers were better than those of the Ni-W base substrates, indicating improved biaxial texturing of the electrodeposited layers. AES analysis of the YBCO/CeO2/YSZ/ED-CeO2/Ni-W revealed that Ni interdiffusion was completely stopped at the first electrodeposited CeO2 layer.
INTRODUCTION It is now well established that biaxially textured crystalline substrates are critical to obtaining superior critical current densities (Jc ) for YBa2 Cu3 O7-δ (YBCO) superconductors. One way to accomplish biaxial texturing in a superconducting material is to grow epitaxial YBCO onto biaxially textured substrates. Rolling-assisted biaxially textured substrate (RABiTS) technology has proven to be very promising for fabricating YBCO-coated conductors [1-3] that can support large currents in high magnetic fields at 77 K. Recently, more attention has been given to paramagnetic Ni-W substrates, instead of Ni, to improve mechanical properties and reduce magnetism. Growth of oxide buffer layers directly on textured paramagnetic Ni-W substrates under typical conditions is challenging because the localized formation of tungsten oxide can deteriorate the properties of oxide buffer layers and YBCO films also. To overcome these adversities, we electrodeposited an additional Ni layer on Ni-W substrate [4,5], which produced a YBCO superconductor with a Jc of 1.49 MAcm-2 at 75.2 K and in a magnetic field of 83 mT. Currently, Ni-W substrates are sulfurized to form a protective sulfide surface layer. Commercial-quality buffer-layer architectures deposited on sufurized Ni-W are typically CeO2/YSZ/Y2O3/Ni-W and CeO2/YSZ/CeO2/Ni-W. At present, the buffer layers are typically deposited by dc magnetron sputtering and pulsed-laser deposition (PLD), which operate at relatively slow deposition rates. In this paper, we report on biaxially textured CeO2 and Sm:CeO2 buffer-layer material prepared inexpensively by an electrodeposition method. Electrodeposition (ED) is a potentially low-cost, nonvacuum, high-rate deposition process that can easily deposit uniform films on large nonplanar substrates.
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EXPERIMENTAL DETAILS The ED of CeO2 was performed from a bath containing 1 g of cerium salt dissolved in 200 mL of deionized water. The Sm-doped CeO2 film was prepared from a bath containing 1 g of cerium salt and 0.006 g Sm salt dissolved
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