Microstructure, texture and critical current of Ag-sheathed 2223 multifilament tapes

An Ag-sheathed 2223 multifilament tape was produced by the powder-in-tube m ethod. The various parts of the tape were heat treated at different tempera tures under reduced oxygen partial pressure. The microstructure and the tex ture were characterized by synchrotron x-ray diffraction and SEM and correl ated with J(c). In the low temperature range (<826 degrees C), the 2223 fra ction and the c-axis alignment of 2223 grains increased with increasing tem perature. A significant increase of J(c) (from 1 to 41 kA cm(-2)) was obser ved in this range, indicating that the phase purity and the texture were th e major controlling factors, In the medium temperature range (826-830 degre es C), the 2223 fraction and the grain alignment tend to saturate, and J(c) remains nearly constant at a level of 40 kA cm(-2). In the high temperatur e range (830-836 degrees C), the 2223 fraction and the grain alignment rema ined unchanged but J(c) decreased with increasing temperature. The drop in J(c) was related to the presence of an amorphous phase and a small amount o f 2201 phase, indicating that the grain connectivity has become the major c urrent-limiting factor. The variations in the filament shape, density and a lignment within the multifilament tape were characterized. The influence of the inhomogeneous structure on J(c) is discussed.