Epitaxial growth of La2Zr2O7 buffer layers for YBa2Cu3O7−δ coated conductors on metallic substrates using pulsed laser deposition

In the present work, La2Zr2O7 (LZO) buffer layers were deposited using pulsed laser deposition (PLD) on various metallic substrates including epitaxial pure Ni on a LaAlO3 (LAO) substrate as well as highly textured Ni–5 at.%W tapes. It is shown that the LZO deposited on pure Ni-buffered LAO exhibits a mixed orientation while LZO on Ni–5 at.%W grows epitaxially. This difference may be explained by the existence of a sulphur superstructure on the surface of Ni–5 at.%W tapes, promoting the epitaxial (0 0 l) nucleation of seed layers. Highly textured YBa2Cu3O7−δ layers were prepared either by using a single buffer layer of LZO or bilayer buffers of CeO2/LZO on Ni–5 at.%W. The superconducting transition temperature (Tc) increases with the LZO thickness, reaching a value of 90 K with a very narrow transition width (1.5 K) for 240 nm thick LZO layers. Inductive Jc measurements at 77 K in self-field show a value of about 0.96 MA/cm2 for the thickest LZO layers, which is comparable to the value observed on standard buffer architectures such as CeO2/YSZ/Y2O3.