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

Abstract

Numerical analyses of YBa 2 Cu 3 O 6:5þx (YBCO) polycrystalline film growth in the metal organic deposition (MOD) process using precursor solution containing metal trifluoroacetates (TFA) have been performed. This process is accompanied with both consuming H 2 O and releasing HF at the growth interface. At first, a one-dimensional numerical growth model of the YBCO was proposed in consideration of the growth kinetics at the interface between the precursor and the YBCO crystalline layers together with the conservation of the gas components, H 2 O and HF, in the precursor layer. This numerical model was treated as a boundary condition for the convective multi-component diffusion equations in the gas region. Subsequently, the convective multi-component diffusion equations and Navier-Stokes equation in the gas region were solved in a two-dimensional manner by the finite difference method. It was found that this numerical model calculation could make a good estimate for the growth rate distribution in the film and the molar fractions of the components in the gas region. Finally, it was confirmed that the supplied water vapor molar fraction dependence, the positional dependence and the inlet gas velocity dependence of the calculated YBCO growth rate were in good agreement with the experimental results.

Control of artificial pinning centers in REBCO coated conductors derived from the trifluoroacetate metal-organic deposition process

“…The details of the reaction in this system were investigated in the early stage of R&D [30][31][32]. Figure 2 shows the The REBCO film epitaxially grows from the interface of the precursor and the top of the buffer layer, and a boundary diffusion layer exists on the surface of the precursor.…”

Highlights of coated conductor development in Japan

“…To achieve higher production rate in the crystallization step of TFA-MOD process, the SRL has proposed and developed the multiturn RTR system with a vertical gas flow system [49]. The vertical gas flow system could realize a smaller thickness of the mass diffusion boundary layer, δ g , for a wider tape [50]; the numerical simulation for YBCO growth shows that the YBCO growth rate is in inverse proportion to δ g , compared to that for the parallel flow, as shown in figure 14. Consequently, the total Relationship between YBCO growth rate, R, and thickness of concentrated gas boundary layer, δ g .…”