Subgrain formation, 211 particle segregation and high-angle 90 degrees boundaries in melt-grown YBaCuO

Microstructural features such as subgrains, Y2BaCuO5 particles, and high-angle boundaries were studied in single- and multiple-domain melt-textured YBaCuO levitators. Subgrains elongated in the c- or a-direction and rectangular in cross section were formed during solidification by cellular growth. Formation of subgrains by combination of a- and c-growth was also observed. Their boundaries were predominantly low-angle, and were not cracked or wetted by second phases. Macrosegregation of Y2BaCuO5 particles developed mainly in the regions formed by c-axis growth. The segregation is related to Y2BaCuO5 particle pushing by the YBa2Cu3O7-x growth front. The structure of 90 degrees high-angle grain boundaries appeared to be similar to that of the low-angle grain boundaries. (C) 1997 Elsevier Science B.V.