Skip to Main Content
The elastic properties of REBCO tape (i.e., REBa2Cu3 O7-d, RE = Y, Sm and Gd) have been investigated by means of diffraction techniques using synchrotron radiation. Total local strain Ahkll, which consists of thermal strain AhklT and lattice strain Ahkl, was analyzed using a microscopic structure model, with two types of microtwin configuration along the tensile axis, i.e., with the  or  crystal axis oriented parallel to the longitudinal direction of the tape. Experimental results were: (a) slope dAh00l/dA is larger than dA0k0l/dA (where A is the external tensile strain), which is attributed to the elastic modulus Ea along the a-axis being smaller than Eb along the b-axis; (b) both dAh00l/dA and dA0k0l/dA are smaller than unity, but dA110l/dA is almost unity depending on the configuration of microtwin; (c) the thermal strain for different planes is different as Ah00T ≠ A0k0T due to the elastic behavior of the superconducting layer being modified because it is constrained by the substrate and the outer metallic layer; and (d) a large Poisson ratio is attributed to this constraint state. It is suggested that the microtwin structure is critical to understand and model this unusual stress/strain behavior.