C-axis oriented YBa2Cu3O7−x thin films are conventionally obtained on polycrystalline substrates, but a- and b-axes are randomly distributed. Due to the weak links at the high-angle grain boundaries in the a–b plane, the critical current density (Jc) are comparatively low, from 103 to 104 A/cm2 (77 K, 0 T), and the Jc decreases in magnetic field in a manner similar to bulk YBa2Cu3 O7−x samples. To reduce weak links at the high-angle grain boundaries, biaxially oriented buffer layers of yttrium stabilized zirconia (YSZ) were formed on polycrystalline, Ni-based alloy by ion-beam assisted deposition (IBAD), and subsequently the a–b plane aligned YBa2Cu3 O7−x film was deposited by laser ablation. Jc of 2.5×105 A/cm2 (77 K, 0 T) and 2.2×104 A/cm2 (77 K, 8.0 T) were obtained. A new method to prevent intergranular weak links has been developed for potential applications using practical polycrystalline substrates.

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Biaxially aligned YBa2Cu3O7−x (YBCO) thin films were produced on polycrystalline Ni-based alloy, by using biaxial yttria-stabilized-zirconia (YSZ) intermediate layers formed by off-normal ion-beam-assisted deposition. Most explicit in-plane alignment was obtained when the YSZ layer formed with the beam-incident angle of 55° from substrate normal. Jc-B characteristics and angular dependence of Jc on the magnetic field were measured. 5.0×105 and 5.5×104 A/cm2 were obtained at 77 K with 0 and 8 T, respectively. The distribution of misorientation angles of in-plane a and b axes between YBCO grains was evaluated by both x-ray pole figure measurement and planar observations of transmission electron microscopy. 50% of the grains had the misorientation angles restricted within ±5°. From the image of dislocations, the elastic strains at grain boundaries were estimated to be relaxed with lower misorientation angle. The high-Jc properties are understood to be obtained by the current paths through low-angle grain boundaries.

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