The Biaxial Strain Dependence of JC of a (RE)BCO Coated Conductor at 77 K in Low Fields

Recently, we designed and commissioned a “crossboard” sample holder that can apply biaxial strains in the plane of a (RE)BCO coated conductor. It allows us to measure the critical current density J
_C
for arbitrary combinations of x- and y-strain. Understanding the in-field, in-plane, biaxial strain dependence of a tape's J
_C
(ε
_xx
, ε
_yy
) is crucial for applications such as CORC or Roebel cables, as the cables are subjected to multiaxial strains during manufacturing and operation. Here, we present experimental data for J
_C
(B, ε
_xx
, ε
_yy
) on a SuperPower SCS4050 APC tape in magnetic fields up to 0.7 T, at 77 K. We also outline a theoretical model for the biaxial strain dependence of J
_C
and use it to parameterize our data and show that the fraction of A-domains and B-domains are roughly equal (f = 0.49 ± 0.03) and that the strain sensitivity of the critical temperature is 1.8 ± 0.1 K%
^-1
and -1.3 ± 0.1 K%
^-1
along their a- and b-axes, respectively, for all the domains in this (RE)BCO tape. For the first time, we show both parabolic and linear strain dependencies of J
_C
in a single tape by changing the angle between the applied strain direction and the twin boundaries in the (RE)BCO layer.