Superconductivity of Sn-Zn Eutectic Alloys

Abstract

An experimental study has been made of the superconducting transitions in Sn-Zn eutectic alloys in the temperature range 3.0-3.7°K, employing magnetization measurements on spherical samples. The samples were about 4 mm in diameter, and the laminar spacing varied from 1 to S/x depending on the speed with which the parent ingot had been cooled from the melt. The measurements showed magnetic isotherms approaching those of a type-I superconductor, but with frozen flux of varying degree. The critical-field-versustemperature relation was similar to that of pure Sn, providing evidence that the laminations behave like a continuous superconducting material. The transition temperature T c was found to decrease with decreasing lamkiar spacing. This effect was compared quantitatively with the predictions of proximity-effect theory. The two significant theoretical parameters derived from the data were p 8 , the effective resistivity ratio of the Sn-rich phase, and T cn , the effective transition temperature of the Zn-rich phase. The large-spacing T c data indicated an effective p s of about 0.12, in reasonable agreement with the expected magnitude. At smaller spacing the experimental T c was higher than expected. Alternatively stated, T en was 2.7°K, which is larger than the accepted Zn transition temperature 0.9°K. *

Persistent current joints between technological superconductors

“…It is worth mentioning that in many eutectic alloys the solute contents and critical fields of the constituent phases are highly sensitive to thermal and mechanical history, and discrepancies in the literature regarding parameters such as critical fields have been attributed to different specimen histories [55]. For example, a critical field of ∼0.1 T was reported by Levy et al for both Sn-Zn and Sn-Cd eutectics [53], whereas other workers reported much lower values for these materials [56]. Similar discrepancies have been reported for Pb-Sb eutectics [53,57].…”

The effect of structure on flux instability and on the superconducting properties of the Mo2Re3Bx–Mo3Re2Bxeutectic

“…Moreover, Levy et al [19] have observed an influence of the interphase boundary area on the critical current-carrying capacity. The Sn-Zn alloy reported by Lutes et al [20] was a specimen of the second type of eutectic. Despite its lamellar structure, the sample behaved like a homogeneous material due to the appearance of a proximity effect.…”

Superconducting Properties of Mo2Re3Bx-Mo3Re2BxEutectic

“…In general, there are two extreme behaviours: properties of eutectic can be a more or less simple sum of the properties of the two phases or it can behave as a completely homogeneous system due to proximity effect. An example of the first case is In-Bi system studied by Currie et al [3], whereas Sn-Zn eutectic reported by Lutes and Clayton [4] behaved like a continuous material with decreasing critical temperature due to the proximity effect. Dobrosavljevic et al [5] observed the effect of proximity on rf surface permeability of Cd-Sn eutectic with superconducting and normal SNSN.…”