Grain Refinement and Enhancement of Critical Current Density in the V_0.60Ti_0.40 Alloy Superconductor With Gd Addition

Abstract

The V-Ti alloys are promising materials as alternate to the commercial Nb-based superconductors for high currenthigh magnetic field applications. However, the critical current density (Jc) of these alloys are somewhat low due to their low grainboundary density. We show here that grain refinement of the V-Ti alloys and enhancement of the Jc can be achieved by the addition of Gd into the system, which precipitates as clusters along the grain boundaries. Both the Jc and the pinning force density ( ) increase with the increasing Gd content up to 1 At. % Gd, where they are more than 20 times higher than those of the parent V0.60Ti0.40 alloy. Introduction of Gd into the system also leads to ferromagnetic (FM) correlations, and the alloys containing more than 0.5 At. % Gd exhibit spontaneous magnetization. In spite of the FM correlations, the superconducting transition temperature increases slightly with Gd-addition.

Coexisting superconductivity and ferromagnetism in the (V0.60Ti0.40)-Gd alloys

“…Similar behaviour is also observed in Ti-rare earth alloys [7]. The SEM images of (V 0.60 Ti 0.40 )-Gd alloys [8] reveal that fine clusters of Gd precipitates along the GBs. The size of the precipitates is < 1.2 m (marked by '⋆' for the Gd2 alloy in the inset to Fig.…”

“…The (V 0.60 Ti 0.40 )-Gd alloys were synthesized by melting the constituent elements (purity ≥ 99.8%) in stoichiometric ratio in a tri-arc furnace under 99.999% pure Ar atmosphere [8]. The nominal compositions are presented in table 1.…”

“…The details of metallography is presented in ref. [8]. The resistivity, and thermal conductivity of the samples were measured in a 9 T Physical Properties Measurement System (PPMS, Quantum Design, USA).…”

“…Rare earth elements are immiscible in the transition metal elements such as titanium and vanadium [6,7]. Recently, we have shown that the addition of Gd to the V 0.60 Ti 0.40 alloy increases the GB density [8]. These GBs along with the Gd precipitates improve the of the V 0.60 Ti 0.40 alloy from 200 Amm −2 to about 800 Amm −2 for 1 at.% Gd in the V 0.60 Ti 0.40 alloy [8].…”

“…Recently, we have shown that the addition of Gd to the V 0.60 Ti 0.40 alloy increases the GB density [8]. These GBs along with the Gd precipitates improve the of the V 0.60 Ti 0.40 alloy from 200 Amm −2 to about 800 Amm −2 for 1 at.% Gd in the V 0.60 Ti 0.40 alloy [8]. The Gd containing V 0.60 Ti 0.40 alloys also exhibit: [8] (i) a ferromagnetic transition at = 295 K, and (ii) slight enhancement of the superconducting transition temperature ( ).…”