Inverted-parabolic and weak strain dependencies on the critical current in practical and oriented REBCO tapes

In the commercial coated conductor tapes, the twinned structure of REBCO (REBa2Cu3O7-d, RE = Y and Gd) is characterized as either or orientation based on the tape length direction. In this study, we investigate the effects of the two different twinned structures on the critical current Ic of the REBCO tapes by combining; transport critical current and synchrotron radiation diffraction measurements. For the tapes with oriented twins, we observed the inverted parabolic strain behavior on the uniaxial strain dependence of Ic. In contrast, the ones with oriented twins showed a weak strain behavior without any maximum appeared in the strain dependence. Such a different uniaxial strain dependence was analyzed by using the one-dimensional twin model with different fractional lengths of A-domains and B-domains of REBCO twins. This model explains the essential features of the different uniaxial strain dependence we observed.