The direct evaluation of the internal strain of biaxially textured YBCO film in a coated conductor using synchrotron radiation

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. In order to elucidate the effect of uniaxial strain on the critical current of practical REBCO tapes (REBa2Cu3O7-d, RE = Y and Gd) fabricated by Superpower and SuNAM, two types of critical current measurements were carried out. In the first, the tape sample was attached directly to a universal testing machine and pulled under a tensile load. In the second, the tape was soldered to a Cu-Be springboard (SB) and then attached to the testing machine and then pushed or pulled in order to apply both tensile and compressive strains to the tape sample. An inverse parabolic behavior was observed for the uniaxial strain dependence of the critical current of both tapes.Using synchrotron radiation, the local strain exerted on the REBCO layer was measured at room temperature under the conditions used for the two techniques for making Ic measurements. On the basis of these room temperature data, the local strain exerted on the REBCO layer at 77 K was numerically evaluated.A one-dimensional chain model for current flow in the REBCO material with fractional lengths of A-domains and B-domains oriented along the uniaxial strain direction is proposed. The model can explain the parabolic strain behavior of the critical current and shows that the strain at which the peak in Ic occurs, is not only determined by pre-compression or pre-tension on the superconductor at the operating temperature, but also by the ratio of the fractional amounts of the two domains.

Section: Evaluation Of Thermal Strain Exerted On Rebco Layer At 77 Kmentioning

confidence: 99%

Mechanism for the uniaxial strain dependence of the critical current in practical REBCO tapes

Osamura¹,

Machiya²,

Hampshire³

2016

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“…For instance, YBCO coated conductors experience large axial stresses in high-field magnets, motors and generators. The YBCO layer breaks at a tensile strain defined by the irreversible strain limit (ε irr ), which should not be exceeded in applications [3][4][5][6]. The irreversible strain limit in YBCO coated conductors under axial compression remains unknown, but most likely exceeds * Contribution of NIST, not subject to US copyright.…”

Section: Introductionmentioning

confidence: 99%

Effect of strain, magnetic field and field angle on the critical current density of Y Ba₂Cu₃O_7−δcoated conductors

Laan

Ekin

Douglas

et al. 2010

127

123

A large, magnetic-field-dependent, reversible reduction in critical current density with axial strain in YBa 2 Cu 3 O 7−δ coated conductors at 75.9 K has been measured. This effect may have important implications for the performance of YBa 2 Cu 3 O 7−δ coated conductors in applications where the conductor experiences large stresses in the presence of a magnetic field. Previous studies have been performed only under tensile strain and could provide only a limited understanding of the in-field strain effect. We now have constructed a device for measuring the critical current density as a function of axial compressive and tensile strain and applied magnetic field as well as magnetic field angle, in order to determine the magnitude of this effect and to create a better understanding of its origin. The reversible reduction in critical current density with strain becomes larger with increasing magnetic field at all field angles. At 76 K the critical current density is reduced by about 30% at −0.5% strain when a magnetic field of 5 T is applied parallel to the c-axis of the conductor or 8 T is applied in the ab-plane, compared to a reduction of only 13% in self-field. Differences in the strain response of the critical current density at various magnetic field angles indicate that the pinning mechanisms in YBa 2 Cu 3 O 7−δ coated conductors are uniquely affected by strain.

“…Diffraction techniques using quantum beams, such as neutron beams and synchrotron radiation, is one effective approach to evaluate thermal residual strain [15][16][17][18][19]. From the change of lattice spacing, the internal strain of the YBCO grains in the coated conductor can be determined directly.…”

Section: Introductionmentioning

confidence: 99%

The reversible strain effect on critical current over a wide range of temperatures and magnetic fields for YBCO coated conductors

Sugano¹,

Shikimachi²,

Hirano³

et al. 2010

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The strain effect on critical current (I c (ε)) in YBa 2 Cu 3 O 7−δ (YBCO) coated conductors was evaluated at temperatures in the range 20-83 K under magnetic fields parallel to the c-axis up to 10 T. The peaked reversible variation of I c with applied uniaxial strain was confirmed in the self-field at all tested temperatures. The strain sensitivity increases with increasing temperature, resulting in a more pronounced reversible suppression with strain at higher temperature. Interestingly, it was found that the peak strain corresponding to the maximum of I c shifts to the compressive side with decreasing temperature. Such a peak shift cannot be explained by a change in the thermal residual strain of the YBCO film, suggesting that the peak strain of the I c (ε) in YBCO coated conductors is not determined only by relaxation of the residual strain. The strain sensitivity of I c (ε) at 60 K becomes greater with increasing magnetic field, while the influence of the magnetic field is much less pronounced at 20 K. The in-field I c (ε), including the compressive strain region as well as the tensile region, shows a double peak behavior at low magnetic field at 77 and 83 K. The temperature and magnetic field effect on I c (ε) in YBCO coated conductors is discussed considering flux pinning within the grains and on grain boundaries.