Island growth of Y₂BaCuO₅ nanoparticles in (211_{∼1.5 nm}/123_{∼10 nm})×N composite multilayer structures to enhance flux pinning of YBa₂Cu₃O_7−δ films

Abstract

A controlled introduction of second-phase Y 2 BaCuO 5 (211) nanoparticles into YBa 2 Cu 3 O 7−␦ (123) thin films was achieved for the first time for the purpose of increasing flux pinning. The island-growth mode of 211 on 123 was utilized to obtain an area particle density >10 11 cm −2 of 211 thick-disk-shaped nanoparticles in individual layers. Composite layered structures of (211 y nanoparticles/123 z )×N were deposited by pulsed laser deposition on LaAlO 3 substrates, with N bilayers ‫ס‬ 24 to 100, y thickness ‫ס‬ 1 to 2 nm, and z thickness ‫ס‬ 6 to 15 nm (assuming continuous layer coverage). With 211 addition, the critical current densities at 77 K were higher at magnetic fields as low as 0.1 T and increased as much as approximately 300% at 1.5 T. The superconducting transition temperature was reduced by approximately 2 to 4 K for 211 volume fraction <20%. Reinitiation of 123 growth after every 211 layer resulted in a smooth and flat surface finish on the films and also greatly reduced surface particulate formation especially in thicker films (∼1 m).

Flux pinning behavior of incomplete multilayered lattice structures in YBa2Cu3O7−d

“…Y211 inclusions in a separate study showed slightly smaller particle formation than Y 2 O 3 likely due to a different growth mechanisms based on lattice mismatch. 3,4 With the CeO 2 patchwork interlayers, it is expected the pinning will be less due to the large size of the inclusions (see Fig. 2).…”

“…3,4 This was accomplished by the subsequent deposition of YBCO (5 -25 nm thick) on top of nonsuperconducting Y 2 BaCuO 5 (Y211)) island-growth particles (ϳ5 -10 nm in diameter) dispersed on the previously deposited YBCO layer. The layering was repeated to provide the desired thickness of the composite film, usually 0.3-3 m thick.…”

Deposition of (Y2BaCuO5/YBa2Cu3O7−x)×N multilayer films on Ni-based textured substrates

“…The RABiTS process is used to introduce a high degree of grain alignment in the Ni-alloys, that is epitaxially transferred into the buffer and 123 film layers [7][8][9][10]. Efforts to improve the J c of coated conductors by increasing 0921 [14,15].…”

Low loss striated YBa2Cu3O7−d coated conductor with filamentary current sharing

“…[6][7][8] Because of this success, the large effort given to the basic architecture of the YBCO coated conductor must begin to be also applied to issues such as ac loss, stability, and magneticflux pinning. [9][10][11][12] The minimization of ac losses is especially critical for the coated conductors, which, being highly aspected, have the potential for high losses in certain applications.…”