2001 Volume 42 Issue 2 Pages 227-232
The effect of the volume fraction of the solid phase (Vf) on coarsening phenomena of Y2BaCuO5 (Y211) particles in Ba–Cu–O melt has been investigated. The volume fraction was changed from 10% to 40% by means of controlling of the nominal composition. The size distribution depends on the nominal composition as well. In the samples with hyperperitectic composition (Vf>37%), two different size groups were recognized. On the other hand, it was not observed in the case of hypoperitectic compositions (Vf<37%). The coarsening rate constant (K) also strongly depends on Vf and classified into two groups even in the hypoperitectic compositions. The samples with lower Vf than 15% reveal a higher coarsening rate constants than those with higher Vf than 20%. The phenomena were qualitatively explained by the difference of coarsening mechanisms. Although the zero Vf assumption in a mean field model can be applied for the samples with lower Vf, it became difficult with increasing of Vf and the diffusion mode for the coarsening is changed from the diffusion through a mean field liquid to those among particles.