Fabrication and growth mechanism of YBCO coated conductors by TFA-MOD process

The study of a rotating method for fabricating Y1Ba2Cu3O7−x films by TFA-MOD

“…The significant influence of process conditions including firing temperature, water vapor pressure, total pressure and gas flow rate on the YBCO growth rate has been demonstrated by several groups [1][2][3], generally both very low and very high growth rate are not beneficial for the qualities of YBCO films. Under conventional conditions, the gas flow is always introduced into the decomposition furnace in a parallel orientation to the film surfaces, then a stable boundary layer will form at the film/gas interface, and its thickness has a close relation with the gas flow rate.…”

“…Under conventional conditions, the gas flow is always introduced into the decomposition furnace in a parallel orientation to the film surfaces, then a stable boundary layer will form at the film/gas interface, and its thickness has a close relation with the gas flow rate. About this situation a theoretical model has been reported [2], it concluded that if the gas flow velocity is relatively slow, the film growth rate-limiting step is the mass transfer in the boundary layer rather than through the unreacted precursor film, especially the diffusion of the gaseous product HF, and approximately the growth rate is inversely proportional to the thickness of the boundary layer. A similar theoretical model of the BaF 2 ex situ process was also proposed by another group [4].…”

Relationship between crystallization process and superconducting properties of YBCO films by TFA–MOD method using starting solution with various compositions

“…In the previous work, we have proposed a one-dimensional analysis for YBCO growth during the crystallization process, considering both diffusion in the gas boundary layer and the growth kinetics at the precursor/YBCO interface [8]. The growth rate of YBCO, R, is described as follows:…”

Numerical Analysis of YBCO Crystal Growth in the TFA-MOD Process

“…4) Consequently, it was considered that the YBCO growth rate was limited by H 2 O and HF diffusions in the gas region. This result allowed as to assume that the diffusivity in the precursor was much larger than that in the gas region and the local equilibrium condition at the precursor/gas interface was maintained.…”

“…The one-dimensional theoretical analysis of the YBCO growth considering multi-component diffusion and growth kinetics at the precursor/YBCO interface was proposed and the estimated growth rate values agreed with experimental ones. 4,5) This analytical solution, however, did not contain the effect of the gas flow velocity variation, and it was not enough to design of the appropriate gas flow system for the actual reaction furnace. In this paper, we propose the numerical model for the YBCO growth which contains two-dimensional gas flow effect.…”