Internal Strain and Mechanical Properties at Low Temperatures of Surround Cu Stabilized YBCO Coated Conductor

The mechanical properties of surround Cu stabilized YBCO coated conductor were assessed at 5.7, 77 and 298 K. The internal strain exerted on the superconducting YBCO layer was directly evaluated under tensile load at low temperatures down to 9.8 K by neutron diffraction techniques. The compressive internal strain, present in the YBCO layer without external load, is the thermally induced residual strain. When the external tensile load was applied, the compressive component of internal strain decreased and changed into tensile. The force-free strain, A_ff, was determined as the strain at which the internal strain becomes zero. The estimated from (200) diffraction data depended weakly on temperatures between 298 and 9.8 K. However, the estimated from (020) data decreased prominently with decreasing temperature.