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

Abstract

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.

Strain Distribution in REBCO-Coated Conductors Bent With the Constant-Perimeter Geometry

“…For the compressive axial strain, a large intrinsic and reversible effect on conductor I c has been observed [25]. An axial compressive strain between 0.5% and 1.0% can reduce the conductor I c for 20% [23,26,27].…”

Review of progress in electromechanical properties of REBCO coated conductors for electric device applications

“…In SmBCO CC tapes, no I c peak was observed during uniaxial tension test showing a monotonic decrease of I c /I c0 with strain in contrast to the case of YBCO CC [47]. On the other hand, in the case of YBCO CC tape, an interesting behavior has been observed showing shifting of the I c peak with magnetic fields as has been described in [33,38,40]. Some reports attributes the J c or I c behavior to the strain dependent pinning mechanisms namely the pinning of Abrikosov-Josephson vortices at grain boundaries at low magnetic field and the pinning of Abrikosov vortices at high magnetic field [48].…”

“…Under magnetic field, different testing apparatus or rig have been developed for the evaluation of electromechanical properties of HTS tapes which includes the Walter spring [37], CuBe bending rig [33,39], and tension-compression bending rig as described in ref [38], [40][41][42]. Fig.…”

“…7 shows the I c /I c0 -strain relation under magnetic field in SmBCO and YBCO CC tapes, respectively. In the cases of SmBCO CC tapes specifically in RCE-SmBCO, the I c /I c0 showed different behavior as compared with YBCO CC case [33,38,40]. In SmBCO CC tapes, no I c peak was observed during uniaxial tension test showing a monotonic decrease of I c /I c0 with strain in contrast to the case of YBCO CC [47].…”

The experiments of 200-meter superconducting DC power cable in Chubu university and the estimation for longer cable cooling

“…We pay attention about the strain of the HTS tapes in the cable because if the tensile strain of the HTS tape is high, the critical current of the HTS tape was reduced [7,8,9]. The thermal contraction of the cable is about 0.3 % and is 60 cm in the 200-meter cable.…”