Abstract
We use atomically resolved scanning transmission electron microscopy and electron energy loss spectroscopy to determine the atomic-scale structural, chemical and electronic properties of artificial engineered defects in irradiated-annealed high temperature superconducting wires based on epitaxial Y(Dy)BCO film. We directly probe the oxygen vacancy defects in both plane and chain sites after irradiation with 18-meV Au ions. The plane site vacancies are reoccupied during post-annealing treatment. Our results demonstrate the dynamic reversible behavior of oxygen point defects, which explains the depression and recovery of self-field critical current and critical temperature in irradiation-annealing process. These findings reveal the strong effect of oxygen vacancies in different sites on the superconductivity properties of irradiated Y(Dy)BCO film, and provide important insights into defects engineering of 2G HTS coil wires.
Highlights
We use atomically resolved scanning transmission electron microscopy and electron energy loss spectroscopy to determine the atomic-scale structural, chemical and electronic properties of artificial engineered defects in irradiated-annealed high temperature superconducting wires based on epitaxial Y(Dy)BCO film
Since the discovery of high temperature superconducting (HTS) rare earth barium copper oxide REBa2Cu3O7-δ (REBCO), significant efforts have been made to enhance its functionalities by introducing artificial vortex pinning microstructures
Irradiation defects have been studied over a full range of atomic, electronic structures and physical properties[17,18,19,20,21], a detailed TEM analysis on the annealing effects is still desirable, especially on the commercial HTS coil wires
Summary
We use atomically resolved scanning transmission electron microscopy and electron energy loss spectroscopy to determine the atomic-scale structural, chemical and electronic properties of artificial engineered defects in irradiated-annealed high temperature superconducting wires based on epitaxial Y(Dy)BCO film. Our results demonstrate the dynamic reversible behavior of oxygen point defects, which explains the depression and recovery of self-field critical current and critical temperature in irradiationannealing process These findings reveal the strong effect of oxygen vacancies in different sites on the superconductivity properties of irradiated Y(Dy)BCO film, and provide important insights into defects engineering of 2G HTS coil wires. The resulting BZO nanocolumns extend along c-axis with a width approximately two times of the superconducting coherence length ξ These nanocolumns give rise to perfect correlated pinning centers for the composite films and produce a significant c-axis-correlated enhancement of critical current density Jc. An alternative approach is to introduce defects structures using electron, proton, neutron, or ion irradiation[7,8,9,10,11]. The TEM work clearly reveals how the low energy heavy ion irradiation and post-annealing process can result in a remarkable improvement of the critical current of AMSC’s standard 2G coil wire
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