Technology Commercialization and Partnerships | BSA 10-23: Metastable Superconducting Cuprate Phase

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Categories: advanced materials, energy

BSA 10-23: Metastable Superconducting Cuprate Phase

BNL Reference Number: BSA 10-23

Patent Status: PCT filed on August 4, 2011

Summary

(a) TEM cross-section of the SSa precipitate embedded in the YBCO+Y248 matrix viewed along the [110] direction. The white rectangle outlines the SSa inclusion. b-d) Structure models of (b) YBa₂Cu₃O₇, c = 1.17 nm (c) YBa₂Cu₄O₈, c = 2.76 nm and (d)SSa phase, c = 3.5 nm. The SSa model cell is formed by insertion of two MO-CuO (M=Y_0.33Ba_0.67) double layers into a Y248 cell.

High-temperature superconductors based on the Y-Ba-Cu-O (YBCO) system (second generation materials) exhibit superior superconducting properties, when optimized, to so-called first generation materials such as Bi-Sr-Ca-Cu-O (BiSCCO). However their sensitivity to oxygen stoichiometry makes them hard to optimize. In particular, YBCO performance is strongly dependent on grain boundaries, degrading when the grain boundary misalignment exceeds about 4° between grains. The result is that YBCO must be biaxially aligned to achieve high performance. This makes manufacture of high-quality material difficult and expensive. Here the inventors have induced growth of a metastable superconducting phase of YBCO that acts as a pinning site and appears less sensitive to grain boundaries than the dominant phase.

Description

Here we use catalytically active (001) ceria buffers to modify the structure of the epitaxial high temperature superconductor YBa₂Cu₃O₇. The modification is achieved by catalytically-assisted synthesis of a previously unknown metastable phase. The new phase, a long-period (3.5 nm) perovskite, intercalates into the YBa₂Cu₃O₇ matrix without negatively affecting the critical temperature of the film. Analysis of electron microscopy and synchrotron X-ray diffraction data allow identification of the phase as a long-period YBa₂Cu₃O₇ derivative formed through short-range cation displacement. The 0.8 micro meter thick films exhibit strong enhancement of the critical current density, reaching a maximum of 4.2 MA/cm2 at 77 K.