ANALYSIS OF PERITECTIC GROWTH MECHANISM OF SUPERCONDUCTING OXIDE WITH FACETED GROWTH INTERFACE

Authors have analized the peritectic growth mechanism of faceted123 crystals from liquid211phases in Y-Ba-Cu-O superconducting oxide mainly by one-dimensional model.In this study，the peritectic growth process of faceted123 crystals was simulated by the two-dimensional numerical model on faceted peritectic growth，which was a coupled method of the authors‘analytical model and Shangguan and Hunt’s numerical model on faceted cell growth.The normal growth rate(RK)of a facet was given by：Rk=ag·DELTATk^2，where DELTATk was the maximum kinetic undercooling on the facet plane，and ag was a kinetic growth constant.The melting rate of 211 particles in the liquid was also given by the above@equation with a kinetic melting constant(Am)instead of ag。The average growth rate Rk(；Rav)on the facet，and diffusion coefficient D in the bulk liquid which should be different from Dg were examined in the calculation.The districutions of residual 211 particles and liquid pools in the faceted123phases of hyper-and hypo-peritectic YBCO(f_&lt；S2110&gt；=0.43，0.32)were calculated with the experimentally obtained initial log-normal distributions of 211particles in the liquid。The calculated results for(A)Rk(Max)，D=5Dg，ag/am=0.1，and(B)Rav，D=2.5Dg，ag/am=0.1，agreed well with the experimental results。This suggested that Dg was different from D，or the growth of faceted interface was affected by the degree of local solute supersaturetion corresponding to the non-uniform distribution of 211particles in the liquid.Further，the following studies should be performed to obtain the precise main controlling parameters(D，Dg，Rk(Max)or Rav，rg/rm等等.)：the optimization of the numerical model and that of the relations between the above parameters and the calculated results，and the more precise experimental works including measurements of the above parameters and solute distribution in the liquid.

Authors have analized the peritectic growth mechanism of faceted 123 crystals from liquid+211 phases in Y-Ba-Cu-O superconducting oxide mainly by one-dimensional model. In this study, the peritectic growth process of faceted 123 crystals was simulated by the two-dimensional numerical model on faceted peritectic growth, which was a coupled method of the authors' analytical model and Shangguan and Hunt's numerical model on faceted cell growth. The normal growth rate (RK) of a facet was given by : Rk=ag・DELTATk^2, where DELTATk was the maximum kinetic undercooling on the facet plane, and ag was a kinetic growth constant. The melting rate of 211 particles in the liquid was also given by the above equation with a kinetic melting constant (am) instead of ag. The average growth rate Rk ( ; Rav) on the facet, and diffusion coefficient D in the bulk liquid which should be different from Dg were examined in the calculation. The districutions of residual 211 particles and liquid pools in the faceted 123 phases of hyper- and hypo-peritectic YBCO (f_<S2110>=0.43,0.32) were calculated with the experimentally obtained initial log-normal distributions of 211 particles in the liquid. The calculated results for (a) Rk (max), D=5Dg, ag/am=0.1, and (b) Rav, D=2.5Dg, ag/am=0.1, agreed well with the experimental results. This suggested that Dg was different from D,or the growth of faceted interface was affected by the degree of local solute supersaturetion corresponding to the non-uniform distribution of 211 particles in the liquid. Further, the following studies should be performed to obtain the precise main controlling parameters (D,Dg, Rk (max) or Rav, rg/rm etc.) : the optimization of the numerical model and that of the relations between the above parameters and the calculated results, and the more precise experimental works including measurements of the above parameters and solute distribution in the liquid.