Biaxial Strain Measurements of JC on a (RE)BCO Coated Conductor

Abstract

For several years it has been possible to measure the uniaxial strain dependence of the critical current density JC(ε) of (RE)BCO coated conductors ((RE)BCO tapes) and a parabolic strain dependence of JC(ε) has been observed. To improve our understanding of how strain affects the electrical and mechanical properties of a SuperPower APC SCS4050 (RE)BCO tape, we have created a biaxial sample holder which can apply arbitrary strains along both the xand y-axes of a (RE)BCO tape simultaneously. It can be used to measure JC for independently controllable applied x and y strains ranging from −0.50% ≤ εx ≤ 0.30% and −0.15% ≤ εy ≤ 0.20% respectively, at 77 K. We present the results of JC measurements over this strain range at 77 K in magnetic fields of up to 0.7 T. We show that we obtain the standard parabolic relationship for JC(εx), with a peak in JC occurring at εxP = −0.01%. We also show that when we apply an additional y strain of εy = −0.08% the peak in JC moves to εxP = 0.4%, which cannot be explained by considering the differential strains produced by non-superconducting components of the tape and sample holder. In addition, the value of JC at the peak increases considerably, by 11%.

The Biaxial Strain Dependence of <italic>J</italic>C of a (RE)BCO Coated Conductor at 77 K in Low Fields

“…The tape's Hastelloy substrate is ~50 μm thick and its (RE)BCO layer is ~1 μm thick and contains artificial pinning centers (APC's). The shape and dimensions of the crossboard on which the sample is mounted have been described previously [16]. Put simply, the crossboard is a sample holder for the tape that is shaped like a cross.…”

“…It has led to the tapes in CORC® cables being wound at 45 ° to minimise the suppression of with that type of strain [1,5]. However, there have been comparatively fewer studies on the effect of the other types of strain on [3,[13][14][15][16] and even fewer on the effect of having strains along multiple axes of a tape simultaneously [13,16]. Single crystal data suggest that the in-plane strain dependence of the critical temperature (and of ) is large (along the a-axis and b-axis) but very weak along the c-axis of (RE)BCO [17].…”

“…This means that biaxial measurements and understanding may provide a very significant improvement in our ability to predict the performance of these tapes in advanced applications with complex strain distributions. To this end, we have recently designed and commissioned a biaxial sample holder known as a 'crossboard' which can apply in-plane, biaxial strains to a tape [16]. The crossboard allows us to measure the in-plane biaxial strain dependence of for arbitrary x-and y-strains (where the x-axis is parallel with the length of the tape and the y-axis is orthogonal to the length of the tape).…”

Magnetization AC losses in multilayer superconducting round cables with coinciding and opposite lay angles

“…Coated conductor (CC) tapes are attractive for use in high-field magnets [1][2][3] as they combine several favourable features: a high upper critical field, a good mechanical strength and a high critical current density of the ReBCO layer [4][5][6][7][8][9][10][11]. However, the current transporting capacity of a single tape is not enough for use in a magnet with reasonable inductance.…”