The strain effect on critical current in YBCO coated conductors with different stabilizinglayers

Abstract

The tensile strain dependences of the critical current(Ic)in YBa2Cu3O7−δ (YBCO) coated conductors fabricated by using the rolling-assisted biaxially textured Ni–Wsubstrates (RABiTS)–pulsed laser deposition (PLD) method were examined at 77 K and inself magnetic field. Cu and stainless steel layers were used as stabilizers to the YBCOcoated conductor, and the effects of stabilizing layers on the strain tolerance ofIc were investigated, compared with the case without a stabilizing layer. The laminationof stabilizer produced an increase in the yield strength and strain tolerance ofIc in coated conductors. All YBCO coated conductors tested showeda reversible strain effect and a peak in the relation betweenIc and applied strain. Thepeak strain of Ic and theirreversible strains for Ic degradation were enhanced when the YBCO coated conductor was laminatedwith a stabilizing layer. For the case laminated with a stainless steel layer,Ic recovered reversibly until the applied strain reached to about 0.5% and showed its peak ata strain of 0.42%, comparing to the case without a stabilizing layer, which were 0.21% and0.18%, respectively. It can be predicted that the lamination of a stabilizing layer produceda significant residual compressive strain to the YBCO film during cooling to 77 K, whichinfluenced the axial strain tolerance of YBCO coated conductors. Therefore, theIc–tensile strain relation in YBCO coated conductors could be explained by a two-stagedeformation; stage I is the region where YBCO film behaves elastically andIc recovers when the stress is released. Stage II is the region whereIc decreases irreversibly attributable to the cracking induced in the YBCO film dueto the significant plastic deformation of the substrate or the stabilizing layer.