| Abstract: |
The critical-current density Jc of an yttrium-barium- copper-oxide (YBCO) coated conductor deposited on a biaxially-textured Ni-5at.%W substrate was measured at 76.5 K as a function of axial tensile strain ε and magnetic field {i}B applied parallel to the YBCO (a,b) plane. Reversibility of Jc with strain was observed up to ε {approximately equal} 0.6 % over the entire field range studied (from 0.05 to 16.5 T), which confirms the existence of an intrinsic strain effect in YBCO coated conductors. Jc vs. ε epends strongly on magnetic field. The decrease of Jc(ε) grows systematically with magnetic field above 2-3 T, and, unexpectedly, the reverse happens below 2 T as this decrease shrinks with increasing field. The pinning force density Fp = Jc × {i}B scaled with field for all values of strain applied, which shows that Fp can be written as K(T,ε)bp(1 – b)q, where {i}p and {i}q are constants, K is a function of temperature and strain, b = B/B*c2 is the reduced magnetic field, and B*c2 is the effective upper critical field at which Fp(B) extrapolates to zero. |
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