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 that can apply arbitrary strains along both the x- and 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% to −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 nonsuperconducting components of the tape and sample holder. In addition, the value of JC at the peak increases considerably by 11%.