Microstructure of V₃Ga superconductingwire using Cu/V with high Ga contents

Hishinuma et al. has established a new Powder-In-Tube (PIT) process using a high Ga content Cu-Ga compound in order to improve the superconducting property of the V₃Ga compound wire. In this study, we investigated the microstructure of this high Ga content Cu-Ga/V composite superconducting wire. Three different contrasts of the matrix, V-Ga phase and Cu-Ga core were observed by SEM observation in the cross section of 19-multifilament wire. The V-Ga phase was confirmed by SEM mapping. The area fraction of V-Ga phase increased when Ga content increased from 30% to 50%. Thin film sample with V-Ga phase for TEM observation was fabricated by FIB. Selected area diffraction pattern was obtained for V matrix, V-Ga phase and Cu-Ga core. The ratio of V to Ga in V-Ga phase was close to V₃Ga according to the EDS result. The interface between V matrix and V-Ga phase was linear, while the interface between Cu-Ga core and V-Ga phase was not linear. On the other hand, there were some granular grains observed in V-Ga phase around Cu-Ga core.