Dependence of superconducting properties of thin films of YBa2Cu3O7−x on structural parameters of the films and substrates

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Abstract
High‐temperature superconducting (HTS) properties such as critical current Jc (77 K) of up to 4×106 A/cm2, microwave surface resistance, Rs (77 K and 50.8 GHz) as low as 15 mΩ and Tc(R=0) of up to 91 K have been measured for YBa2Cu3O7−x, YBCO, layers prepared by pulsed laser deposition on MgO and (11̄02) Al2O3 buffered with yttrium stabilized zirconia (YSZ). The following x‐ray structural parameters have been measured: percentage of residual (200) or (103) lines, value of c‐axis parameter, percentage of (111) unwanted lines in (100) YSZ buffer layers, ratio of 〈100〉 to 〈110〉 orientation in the basal plane as determined by double crystal diffraction phi‐scan and full width half maximum (FWHM) of (005) rocking curve. It was found that the most critical structural parameter is the substrate quality and 100% 〈100〉 basal plane orientation of the individual grains.