Ex-situ post-deposition processing for large area Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/ films and coated tapes

Ex-situ post-deposition reaction processing is considered a promising alternative to in-situ physical vapor deposition techniques for coated Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/ conductor development. It was reported recently that attempts at ex-situ processing of long Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/ precursor tapes resulted in an inhomogeneous growth rate over the tape length and rather poor properties for the whole sample. We performed a set of experiments in order to clarify the mechanisms for the ex-situ processing of large area films and estimate properties of long coated conductors manufactured by the ex-situ technique. It was found that rate limiting step of ex-situ growth of Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7/ is removal of the reaction product, hydrofluoric acid, by both gas diffusion and convection in the reaction atmosphere. We report on a quantitative model that well describes the observed growth rates for films with various areas.