Domain structure and Y2BaCuO5 distribution in single- and multiple-domain melt-textured YBaCuO

Microstructural features such as subgrains, Y2BaCuO5 particles, ana 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 a Y2BaCuO5 particle pushing by the YBa2CU3O7-x growth front, in combination with coarsening by Ostwald ripening and agglomeration. The structure of 90 degrees high-angle grain boundaries appeared to be similar to that of the low-angle grain boundaries. (C) 1997 Academic Press Limited.