Critical current density in filamentary (Nd, Sm, Eu, Gd)–Ba–Cu–O superconductors prepared by a solution spinning method

doi:10.1016/S0921-4534(99)00608-5

Physica C: Superconductivity

Volume 330, Issues 1–2, 1 March 2000, Pages 51-57

https://doi.org/10.1016/S0921-4534(99)00608-5 Get rights and content

Abstract

The filamentary (Nd, Sm, Eu, Gd)–Ba–Cu–O (LRE123) precursor was prepared by the solution spinning method, through a homogeneous aqueous solution containing mixed acetates of Nd, Sm, Eu, Gd, Ba, and Cu, poly(vinyl alcohol) and organic acids. The filamentary sample was partially melted at 980°C in flowing 0.1% O₂+Ar and oxygenated under various conditions. The transport critical current density (J_c) for the samples was examined in magnetic fields up to 10 T at 77 K. The highest J_c value of more than 1×10⁴ A/cm² at 77 K and 9 T was achieved for the filamentary Nd_0.295Sm_0.295Eu_0.295Gd_0.295Ba_2.12Cu_3.09O_x superconductors by controlling the oxygenation conditions.

Introduction

It is well-known that Nd–Ba–Cu–O (Nd123) bulk superconductors prepared by the oxygen-controlled melt growth (OCMG) process exhibit high T_c and the secondary peak effect accompanied by a large critical current density (J_c) in a high magnetic field region at 77 K. The high J_c and its peak effect in the field dependence of J_c for the OCMG Nd123 samples were explained by the field induced flux pinning of weak superconducting regions caused by Nd–Ba substitution [1]. For practical applications of a high T_c superconducting magnet at 77 K, high J_c in a high magnetic field must be achieved in the superconducting wire. We have studied the preparation of filamentary Nd123 superconductors by the solution spinning method and the OCMG method [2]. The filamentary Nd123 superconductor produced in flowing 1% O₂+Ar exhibited higher J_c values at 77 K and 10 T than that for the filamentary Y123 superconductor [3]. The highest J_c value of 3.5×10⁴ A/cm² at 77 K and 0 T and more than 10⁴ A/cm² at 77 K and 2 T was achieved for the filamentary Nd_1.18Ba_2.12Cu_3.09O_x superconductors partially melted in flowing 0.1% O₂+Ar [4].

Recently, it is experimentally confirmed that the OCMG process is also effective in achieving high J_c and T_c values for LRE–Ba–Cu–O in which LRE site is compounded with two, three, and four LRE elements [5], [6]. An improvement of magnetically determined J_c value such as 6×10⁴ A/cm² at 77 K and 1.2 T was reported in Nd_0.25Sm_0.25Eu_0.25Gd_0.25Ba₂Cu₃O_x composite [7].

We have attempted a preparation of filamentary LRE123 (LRE=Nd, Sm, Eu, Gd) superconductors with high J_c value by solution spinning method and the OCMG process [8]. While the OCMG process for the filamentary LRE123 superconductors was more complicated than that for the filamentary Nd123 superconductors, a dense and well-aligned texture was obtained by controlling the heating condition and the initial composition. In contrast with filamentary Nd123 superconductors having a few voids in the step-like bulky grains, the dense texture of the filamentary LRE123 superconductors is beneficial for practical applications such as superconducting magnets and cables.

In this paper, we report the effect of a two-step heat treatment for oxygenation on the field dependence of J_c at 77 K for filamentary Nd_0.295Sm_0.295Eu_0.295Gd_0.295Ba_2.12Cu_3.09O_x superconductors partially melted in flowing 0.1% O₂+Ar.

Section snippets

Experimental procedure

The filamentary LRE123 precursor was produced by dry spinning through a homogeneous aqueous solution containing mixed acetates of Nd, Sm, Eu, Gd, Ba and Cu, poly(vinyl alcohol), propionic acid and 2-hydroxy isobutyric acid. An acetate mixture with a nominal composition of Nd:Sm:Eu:Gd:Ba:Cu=0.295:0.295:0.295:0.295:2.12:3.09 was dissolved in the solution. Then we concentrated the solution to obtain a stable viscous homogeneous spinning dope. The dope was extruded as a filament into a hot air zone

Results and discussion

The calcined filamentary samples were partially melted in flowing 0.1% O₂+Ar. The samples were then heated at various temperatures ranging from 400°C to 600°C (400°C (sample 1), 500°C (sample 2), 600°C (sample 3)) for 5 h, rapid-cooled to 340°C and maintained for 10 h, followed by furnace cooling to room temperature in flowing pure oxygen gas for oxygenation of the samples. The sample had a mixed structure consisting of the orthorhombic 123 system and the 211 phase. The size of the 211 phase

Conclusion

Filamentary LRE(Nd, Sm, Eu, Gd)123 superconductors were fabricated by the solution spinning and melt growth process in flowing 0.1% O₂+Ar. A two-step treatment was employed for the oxygenation. J_c was measured in magnetic fields up to 10 T at 77 K. The J_c–B behavior was strongly dependent on the oxygenation conditions and the pinning properties were examined by an extended analysis of the volume pinning force F_p=J_c×B. The highest value of more than 1×10⁴ A/cm² at 77 K and 9 T was achieved for

References (13)

M. Takahama et al.
Physica C
(1998)
T. Saitoh et al.
Physica C
(1997)
M. Nakamura et al.
Physica C
(1996)
S.I. Yoo et al.
Appl. Phys. Lett.
(1994)
T. Goto et al.
Jpn. J. Appl. Phys.
(1997)
T. Kimura et al.
IEEE Trans. Appl. Supercond.
(1999)

There are more references available in the full text version of this article.

Cited by (27)

Effect of Rb<inf>2</inf>CO<inf>3</inf> and Cs<inf>2</inf>CO<inf>3</inf> on MgB<inf>2</inf> in polycrystalline bulk samples
2023, Physica C: Superconductivity and its Applications
MgB₂ polycrystalline bulk samples were prepared by means of reaction of Mg and B powders mixed with various amounts of Rb₂CO₃ or Cs₂CO₃ powders. The a-axis lattice parameter is decreasing in parallel with the increase of the carbonate addition level, more in the case of Cs₂CO₃ than Rb₂CO₃, while the c-axis parameter marginally increases. The extent of the a-axis contraction appears to be larger than expected from carbon doping only. The superconducting transition temperature of MgB₂ decreases upon addition of the carbonate compounds. EDS analysis shows that some Cs and maybe Rb are still present in the samples after reaction. Whereas no evidence was found for segregation of these elements in impurity phases, it is not possible to ensure that Rb and/or Cs actually enter the MgB₂ lattice due to the low amounts used in this study. The critical current density of MgB₂ was improved both in self field and under low applied magnetic field for T ≤ 30 K, with optimum results for 1 mol.% Rb₂CO₃ addition and 1 mol.% Cs₂CO₃ addition respectively. The absolute value of the pinning force is hardly improved. The flux pinning mechanism at low field is similar for all samples and corresponds to the point pinning model behavior but at reduced fields b > 1 the pinning force dependence points towards an increasing contribution of surface pinning. This indicates that the j_c improvement at low fields is due to other effects than enhanced flux pinning. It is possible that Rb₂CO₃ and Cs₂CO₃ induce a transient liquid phase during the reaction between the Mg and B powders, which improves the crystallinity and thus the critical current density at low field.
Various effects of aliphatic amino acids on the critical current of the MgB<inf>2</inf> superconductor
2020, Physica C: Superconductivity and its Applications
Carbon-doped MgB₂ polycrystalline bulk samples were prepared by reacting mixtures of Mg and B powders, with and without 0.5 wt.% of the amino acids glycine, alanine, valine, leucine or isoleucine. The amount of carbon introduced into the MgB₂ structure depends on the amino acid and is surprisingly higher for glycine, which has the lowest carbon content among the aliphatic amino acids. The critical temperatures of samples doped with all kinds of additives were lower than for the undoped sample. The critical current density was influenced by the additives to different extents, alanine, valine and leucine yielding the best results. The pinning force is also larger for these additives at T < 30 K. An analysis of the normalized flux pinning force behavior leads to the conclusion that point pinning is predominant in all samples.
Increase of the critical current density of MgB<inf>2</inf> superconducting bulk samples by means of methylene blue dye additions
2019, Physica C: Superconductivity and its Applications
MgB₂ bulk samples were made by means of reaction of elemental Mg and B powders with or without additions of methylene blue trihydrate, a carbon source, which melts at high temperature upon decomposition. The T_c of the MgB₂ phase as well as its a-axis parameter were decreased as a result of carbon doping, whereas the c-axis parameter only shows a weak tendency for increasing. The critical current density of MgB₂ was improved both in self-field and under applied magnetic field for T ≤ 25 K, the best results being obtained for 0.5–1.0 wt.% methylene blue trihydrate addition. Based on normalized flux pinning force (f(b)) versus reduced field (b) plots, it was found that the flux pinning mechanism at low reduced field is similar for all samples, with a behavior close to the predictions of the point pinning model. However, for b larger than 1, the behavior of f(b) is significantly altered in the methylene blue trihydrate added samples and tends towards the surface pinning model. Methylene blue trihydrate is an efficient carbon source and furthermore provides a liquid phase between 200 °C and 450 °C, which may have some influence on the critical current density improvements at low field.
Critical current density improvements in MgB<inf>2</inf> superconducting bulk samples by K<inf>2</inf>CO<inf>3</inf> additions
2018, Physica C: Superconductivity and its Applications
MgB₂ bulk samples with potassium carbonate doping were made by means of reaction of elemental Mg and B powders mixed with various amounts of K₂CO₃. The T_c of the superconducting phase as well as its a-axis parameter were decreased as a result of carbon doping. Potassium escaped the samples during reaction. The critical current density of MgB₂ was improved both in self field and under applied magnetic field for T ≤ 30 K, with optimum results for 1 mol% K₂CO₃ addition. The normalized flux pinning force (f(b)) shows that the flux pinning mechanism at low field is similar for all samples, following the predictions of the point pinning model. In contrast the behavior of f(b) is significantly altered at reduced fields (b) larger than unity by K₂CO₃ additions, tending towards surface pinning. Besides providing carbon, another effect of K₂CO₃ may originate from the presence of a transient liquid phase that appears to improve the crystallinity and thus the critical current density at low field.
Influence of iridium doping in MgB<inf>2</inf> superconducting wires
2018, Physica C: Superconductivity and its Applications
MgB₂ wires with iridium doping were manufactured using the in-situ technique in a composite Cu-Nb sheath. Reaction was performed at 700 °C, 800 °C or 900 °C for 1 h in argon atmosphere. A maximum of about 1.5 at.% Ir replaces Mg in MgB_2. The superconducting transition temperature is slightly lowered by Ir doping. The formation of IrMg₃ and IrMg₄ secondary phase particles is evidenced, especially for a nominal stoichiometry with 2.0 at.% Ir doping. The critical current density and accommodation field of the wires are strongly dependent on the Ir content and are generally weakened in the presence of Ir, although the effect is less pronounced at lower temperatures.
Attempts at doping indium in MgB<inf>2</inf>
2016, Physica C: Superconductivity and its Applications
Indium (In) doped MgB₂ polycrystalline samples were prepared by solid-liquid phase reaction in Ar. After reaction at 800 °C, less than 1 at.% Mg was replaced by In in the MgB₂ phase, without significant influence on its lattice parameters and only a slight decrease of its superconducting transition temperature. For all studied In concentrations in the nominal composition, the formation of InMg was evidenced by X-ray diffraction. The critical current density and accommodation field of the wires are decreased in the samples containing In. The flux pinning mechanism can be described by surface pinning in both the doped and undoped samples.

View all citing articles on Scopus

View full text

Critical current density in filamentary (Nd, Sm, Eu, Gd)–Ba–Cu–O superconductors prepared by a solution spinning method

Abstract

Introduction

Section snippets

Experimental procedure

Results and discussion

Conclusion

Physica C

Physica C

Physica C

Appl. Phys. Lett.

Jpn. J. Appl. Phys.

IEEE Trans. Appl. Supercond.