Bi‐textured YBa2Cu3O7−δ (YBCO) thin films with different ratios of [100] to [110] grains can be grown controllably on (100) yttria‐stabilized ZrO2 (YSZ) substrates using pulsed laser deposition. It was found that the ratio of [100] to [110] grains was determined predominantly by the laser fluence. By comparing the transport and intragranular critical currents, it is shown that the 45° grain boundaries (GBs) are only correspondent to about 18x reduction in Jc across polycrystalline bi‐texture samples. A percolation simulation was carried out to find out the relationship between Jc reduction across a single GB and in a polycrystalline thin film sample with many GBs. The calculated results were compared with the experimental data. The transport critical current for different films were also studied in the presence of applied magnetic field.

The instantaneous oxygen content of YBa2Cu3O7−δ thin films was measured during pulsed laser deposition by in situ resistance measurements. The oxygen deficiency (δ) of the surface layer was found to be ∼0.835 during the laser plume and increase to 0.90 when the plume was turned off. Using a theoretical fit it was found that the thickness of the oxygen‐rich layer at the surface increased with increasing film thickness and saturated at ∼300 Å for thick films. The out‐diffusion of oxygen in the absence of the laser plume can be well characterized by a simple diffusion equation, with a diffusivity of D=1.5×10−13 cm2/s. On the other hand, the in‐diffusion of oxygen during the laser plume occurs with a diffusivity of D≳10−8 cm2/s. The vastly different diffusivity is due to the presence of activated atomic oxygen in the laser plume.

The J(c) of a polycrystalline film was studied experimentally and modeled by a percolation calculation. The superconducting thin film was modeled as a single layer of grains so that current limitation was considered as a linear optimization problem. Since the degree of in plane a-axis texturing of the grains in in situ Y-Ba-Cu-O thin films was known, the critical current densities in polycrystalline superconducting thin films could be calculated. Comparison of transport and SQUID critical current densities from the experimental data and the calculated values in terms of intragrain critical current density, gave the estimation of J(c) reduction across the 45-degrees grain boundary.