Effect of the cooling rate on the pore distribution in melt-processed YBa2Cu3O7–y superconductor

To understand the pore formation and its distribution in melt-textured YBa2Cu3O7–y, the cooling rate through the peritectic temperature was changed. The top-seeded melt-processed YBa2Cu3O7–y samples were prepared at various cooling rates (1 °C/h to 100 °C/h) from 1020 °C to 960 °C. It was found that the sample dimension and bulk density were a function of the cooling rate; the higher bulk density at lower cooling rate. It is attributed to the easier oxygen diffusion into the samples during solidification at slow cooling rate. The polished microstructural investigation showed that the interior pore density of the sample was higher than that of the edge of the sample. Pore-free regions near the sample surface due to a pore filling by a liquid diffusion were observed in all samples. The size of the pore-free region of the sample prepared at a lower cooling rate was larger.