YBa2Cu3O7-δ bicrystal grain boundary Tc microstructure

We use an S_αS_βISβ_Sα tunneling/proximity-effect model with measured YBa₂Cu₃ O_7-δ (YBCO) grain boundary function (GBJ) normalized critical current temperature dependence η(T)=I_c(T)I_c(O) to infer microstructural transition temperature profiles T_c(x) for bicrystal GBJs with various misorientation angles θ. We discuss the rationale for selecting an optimum value for a numerical analysis parameter ε (associated with the S_αS_β interface T _c discontinuity). We determine the extent to which inferred T _c(x) profiles vary with ±20% rms deviations from nominal values for the fixed input parameters whose a priori values are not precisely known. This sensitivity analysis shows that specified T _c locations can be determined with ⩽±1 nm precision for T_c<60 K. Finally, we present new inferred T _c(x) profiles for bicrystal junctions with θ=24° and 32° and compare these profiles with those of bicrystal JJs with θ=19° and 36.8° which we previously reported. Our inferred T_c(x) profiles for these functions exhibit a clear correlation with θ: as θ increases so does the extent of the grain boundary region with suppressed T_c. This expected result gives us confidence that our approach should prove useful as a tool for elucidating the structure and properties of high temperature superconductors