Aqueous Chemical Solution Deposition of Novel, Thick and Dense Lattice-Matched Single Buffer Layers Suitable for YBCO Coated Conductors: Preparation and Characterization

Abstract

In this work we present the preparation and characterization of cerium doped lanthanum zirconate (LCZO) films and non-stoichiometric lanthanum zirconate (LZO) buffer layers on metallic Ni-5% W substrates using chemical solution deposition (CSD), starting from aqueous precursor solutions. La2Zr2O7 films doped with varying percentages of Ce at constant La concentration (La0.5CexZr1−xOy) were prepared as well as non-stoichiometric La0.5+xZr0.5−xOy buffer layers with different percentages of La and Zr ratios. The variation in the composition of these thin films enables the creation of novel buffer layers with tailored lattice parameters. This leads to different lattice mismatches with the YBa2Cu3O7−x (YBCO) superconducting layer on top and with the buffer layers or substrate underneath. This possibility of minimized lattice mismatch should allow the use of one single buffer layer instead of the current complicated buffer architectures such as Ni-(5% W)/LZO/LZO/CeO2. Here, single, crack-free LCZO and non-stoichiometric LZO layers with thicknesses of up to 140 nm could be obtained in one single CSD step. The crystallinity and microstructure of these layers were studied by XRD, and SEM and the effective buffer layer action was studied using XPS depth profiling.

Sol–gel deposition of high-performance Re0.2Ce0.8O2/La2Zr2O7 composite buffer layers on Ni–W tapes for YBCO coated conductors

“…It is known that the buffer layers such as CeO 2 , yttriumstabilized ZrO 2 (YSZ), Y 2 O 3 , SrTiO 3 (STO), and La 2 Zr 2 O 7 (LZO) play an important role in the architecture of the YBCO-coated conductor [2][3][4]. In order to obtain YBCOcoated conductor with high critical current (I c ), buffer layers should have certain properties, including a high chemical stability, a good capability of blocking interdiffusion, and the close lattice parameter to YBCO phase [5][6][7]. Recently, buffer layers with the composite architecture such as Y 2 O 3 /YSZ/CeO 2 and CeO 2 /LZO and a single structure such as LZO and STO have been developed for epitaxial growth of YBCO film by vacuum or non-vacuum deposition techniques [4,[8][9][10].…”

“…Compared with LZO, CeO 2 has better chemical compatibility with the YBCO film [5,14]. Therefore, the CeO 2 buffer layer or the CeO 2 /LZO composite buffer layer has been extensively investigated.…”