Nucleation and growth rate influence on microstructure and critical currents of TFA-YBa2Cu3O7 under low-pressure conditions

The effects of variable conversion parameters on the microstructure and critical currents of TFA-derived YBa2Cu3O7 (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-H2O-P-O2, 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-flow-water-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