TEM OBSERVATIONS OF MELT-TEXTURED ND123 SUPERCONDUCTORS

Transmission electron microscopy (TEM) observations have been conducte d on melt-textured Nd123 crystals. Some structural defects in the Nd12 3 matrix and Nd123/Nd422 interfaces and the detailed microstructure of crystal boundaries are investigated. Two styles of stacking faults re sulting from the insert atomic layer and the disappearance of the inse rt atomic layer have been observed. The origin of these stacking fault s is discussed. A new lattice matching state has been discovered in th e low-angle Nd422/Nd123 interfaces. Nd123 lattices near Nd422/Nd123 in terfaces change their c-axes in order to minimize the misorientation b etween the c-axis of Nd123 lattice and that of Nd422 lattice, Rich edg e dislocations in the Nd123 matrix are induced by the Nd123 crystal la ttice adjustment near Nd422/Nd123 interfaces. The whole pinning effect of Nd422 precipitate is predicted to depend on the competition of two pinning sites due to low-angle Nd422/Nd123 interfaces with alleviated stress and rich edge dislocations associated with the Nd123 lattice r egulation, respectively. (C) 1998 Elsevier Science B.V.