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The effects of variable conversion parameters on the microstructure and critical currents of TFA-derived YBa 2 Cu 3 O 7 (YBCO) films annealed under low-pressure conditions were investigated, accompanied by the analysis of their relationship with the nucleation process and the growth rate. It is found that non-c-axis oriented YBCO grains are formed under high supersaturation conditions, i.e., by increasing oxygen pressure, water pressure, or temperature. The optimal P H 2 O -P O 2 window for preparation of completely c-axis oriented YBCO films expands as the total pressure rises from 50 to 100 mbar due to the decrease of supersaturation at enhanced total pressure; the corresponding maximum growth rate is only slightly increased up to 0.6 nm/s. Additionally, it is shown that the gas flow needs to be high enough to avoid random nucleation of YBCO grains. A single gas-flowwater-pressure diagram, showing simultaneously the film-growth rate, allows visualizing the cross-linked influence of processing parameters to achieve c-axis oriented YBCO films with J c above 1 MA/cm 2 in one single growth step.

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