A Modified Lattice Model of the Reversible Effect of Axial Strain on the Critical Current of Polycrystalline REBa₂Cu₃O_{7−δ Films}

The strain effect on the critical current is one of the most important properties for polycrystalline YBa₂Cu₃O_7−δ (REBCO, RE: rare earth) films, in which the reversible effect is intrinsic in the range of strain 0 and the irreversible strain ε_irr. By introducing the applied strain, a modified lattice model combining the strain and misorientation of grain boundaries (GBs) in the REBCO film is developed. A good agreement of the calculation on the lattice model with the experimental data shows that the lattice model is able to well describe the reversible effect of axial strain on the critical current of the REBCO film, and provides a good understanding of the mechanism of the reversible effect of the strain. Moreover, the effects of the crystallographic texture of the REBCO film and the residual strain ε_r on the variation of the critical current with the applied strain are extensively investigated. Furthermore, by using the developed lattice model, the irreversible strain ε_irr of the REBCO film can be theoretically determined by comparing the calculation of the critical current-strain curve with the experimental data.