Enhancement of functional properties of V0.6Ti0.4 alloy superconductor by the addition of yttrium

Abstract

We show here that yttrium is immiscible and precipitates with various sizes in the body centered cubic V0.6Ti0.4 alloy superconductor. The number and size of the precipitates are found to depend on the amount of yttrium added. Precipitates with various sizes up to 30 μm are found in the V0.6Ti0.4 alloy containing 5 at. % yttrium. The large amount of line disorders generated by the addition of yttrium in this alloy is found to be effective in pinning the magnetic flux lines. While the superconducting transition temperature increases with the increasing amount of yttrium in the V0.6Ti0.4 alloy, the critical current density is maximum for the alloy containing 2 at. % yttrium, where it is more than 7.5 times the parent alloy in fields higher than 1 T. We found that the effectiveness of each type of defect in pinning the flux lines is dependent on the temperature and the applied magnetic filed.

Strong paramagnetic response in the superconducting state of Y-containing V0.6Ti0.4 alloys

“…Detailed microscopy studies on Y0 and Y1-Y5 alloys can be found elsewhere [8,22,25]. Here, we highlight some important points required for the present study.…”

“…Our previous studies show that inhomogeneous flux pinning together with significant flux creep are the reasons behind the HFPME in V-Ti alloys [7], and that the absence of this phenomenon in V 0.6 Ti 0.4 is due to its low flux creep [7]. Recently, we have shown that the rare earths (RE) are immiscible in the V 0.6 Ti 0.4 phase and precipitate along the grain boundaries [21,22]. We also observed that the distribution of the size of precipitates depends on the amount of RE element present in the alloy [22].…”

“…Recently, we have shown that the rare earths (RE) are immiscible in the V 0.6 Ti 0.4 phase and precipitate along the grain boundaries [21,22]. We also observed that the distribution of the size of precipitates depends on the amount of RE element present in the alloy [22]. Moreover, the stress fields created by these precipitates generate dislocations.…”

“…Moreover, the stress fields created by these precipitates generate dislocations. The mixed microstructure is also responsible for the enhancement of critical current density (J c ) in these alloys [21,22]. The pinning strength of different kinds of defects depends on the temperature and magnetic field [22,23].…”

“…The mixed microstructure is also responsible for the enhancement of critical current density (J c ) in these alloys [21,22]. The pinning strength of different kinds of defects depends on the temperature and magnetic field [22,23]. Therefore, an inhomogeneous distribution of flux line pinning may be expected in REcontaining V-Ti alloys.…”