Influence of precursor calcination parameters on the critical current density of Bi-2212 superconductors

Sager, D.; Meier, Lorenz; Gauckler, Ludwig J.; Chen, M.

doi:10.1016/j.physc.2005.11.017

Cited by 5 publications

(9 citation statements)

References 31 publications

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“…This is due to greatly suppressed cation diffusion over a long length scale. On the other hand, liquid formation reduces the homogeneity of the calcined powder because a large amount of impurity phases with large particle sizes form from the partial-melt [19]. Excessive and uncontrolled grain growth was also observed with the presence of liquid [19].…”

Section: Calcination and Phase Transformationsmentioning

confidence: 99%

“…Many methods have been developed to produce Bi-Sr-Ca-Cu-oxide precursors. The solid-state route starts with raw materials such as oxides, carbonates, nitrates or hydroxides and goes through a series of calcination and pulverizing processes [17][18][19][20]. The final properties of Bi2212 powders, including phase assemblage, grain size and homogeneity, depend on the stoichiometry and particle size of the starting materials [21][22][23], calcination conditions [19] and the pulverizing process, such as grinding and ball milling.…”

Section: Introductionmentioning

confidence: 99%

“…The solid-state route starts with raw materials such as oxides, carbonates, nitrates or hydroxides and goes through a series of calcination and pulverizing processes [17][18][19][20]. The final properties of Bi2212 powders, including phase assemblage, grain size and homogeneity, depend on the stoichiometry and particle size of the starting materials [21][22][23], calcination conditions [19] and the pulverizing process, such as grinding and ball milling. In previous studies, the common size of the starting material powders was micrometers or larger, resulting in chemical inhomogeneities and incomplete carbon release, and thus requiring a repetition of calcination and pulverizing processes.…”

Section: Introductionmentioning

confidence: 99%

“…These studies propose requirements on stoichiometry, phase purity, homogeneity and carbon content of Bi2212 precursors in the green wire. Yet, far fewer studies have discussed the effect of precursor stoichiometry on wire performance [23,36], and most of those either focused solely on the synthesis process and properties of Bi2212 bulk materials [24,[37][38][39][40][41][42] or studied precursor properties by comparing superconducting tapes/ thick films that had varying methods, geometries and substrates [10,19,29,43,44]. Furthermore, recent over-pressure (OP) processing has effectively reduced gross microstructural porosity in Bi2212 wire, resulting in greatly increased critical current density ( J c ) [45].…”

Section: Introductionmentioning

confidence: 99%

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High critical current density Bi₂Sr₂CaCu₂O_x/Ag wire containing oxide precursor synthesized from nano-oxides

Zhang

Johnson

Naderi

et al. 2016

Supercond. Sci. Technol.

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Bi2Sr2CaCu2Ox (Bi2212)/Ag-alloy wires are manufactured via the oxide-powder-in-tube route by filling Ag/Ag-alloy tubes with Bi2212 oxide precursor, deforming into wire, restacking and heat treating using partial-melt processing (PMP). Recent studies propose several requirements on precursor properties, including stoichiometry, chemical homogeneity, carbon content and phase purity. Here, nanosize oxides produced by nGimat’s proprietary NanoSpray CombustionTM process are used as starting materials to synthesize Bi2212 oxide precursors via solid-state calcination. Oxide powders for wire fill (precursor powder) with precisely controlled stoichiometry and chemical homogeneity containing over 99 vol% of single Bi2212-phase are synthesized. Alkaline-earth cuprate are found to be the only impurity phase in the precursor powders. Phase transformation, carbon release and grain growth during calcination are studied through a series of quench studies. Effects of particle size, surface area, stoichiometry, chemical homogeneity and microstructures of the starting materials on Bi2212 formation and wire transport properties are discussed. Small particle size, high surface area and short diffusion length of the starting materials result in a rapid and homogeneous phase transformation to Bi2212, along with an early and rapid carbon release. The residual carbon in the precursor powder is between 50 and 90 ppm. The strong dependence of transport Jc on precursor stoichiometry indicates that compositional variations within precursor powders should be less than 1.5 mol%. Two Bi-rich and Ca-deficient stoichiometries give higher wire transport critical current density, with the highest being 2520 A mm−2 (4.2 K, 5 T) after 1 bar PMP and 4560 A mm−2 (4.2 K, 5 T) after 100 bar overpressure (OP) processing. The low residual carbon content results in smaller and fewer voids within an OP-processed wire filament. Bi-rich and Ca-deficient stoichiometries and small compositional variations within precursor powders may be a method for engineering uniformly-distributed and high-density Bi2201 intergrowths within Bi2212 grains after PMP.

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Section: Calcination and Phase Transformationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

High critical current density Bi₂Sr₂CaCu₂O_x/Ag wire containing oxide precursor synthesized from nano-oxides

Zhang

Johnson

Naderi

et al. 2016

Supercond. Sci. Technol.

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show abstract

“…Although a variety of approaches are used to synthesize oxide precursors [27][28][29][30][31][32][33][34][35], the OPIT route has important shortcomings that limit the final Bi2212 wire performance. Bubbles and voids form and evolve during partial melt because of low tap density of the green wire and carbon residue in the Bi2212 oxide precursor [13,26,[36][37][38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Formation of Bi₂Sr₂CaCu₂O_x/Ag multifilamentary metallic precursor powder-in-tube wires

Zhang

Koch

Schwartz

2016

Supercond. Sci. Technol.

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Previously, a metallic precursor (MP) approach to synthesizing Bi2Sr2CaCu2Ox (Bi2212), with a homogeneous mixture of Bi, Sr, Ca, Cu and Ag was produced by mechanical alloying. Here, Bi2212/Ag round multifilamentary wire is manufactured using a metallic precursor powder-in-tube (MPIT) process. The MP powders were packed into a pure Ag tube in an Ar atmosphere and then sealed. After deformation, multifilamentary round wires and rolled tapes were heat treated in flowing oxygen through three stages: oxidation, conversion and partial-melt processing (PMP). Processing-microstructure-property relationships on 20–50 mm long multifilamentary round wires and rolled tapes were studied extensively. It is shown that conventional wire deformation processes, optimized for oxide-powder-in-tube wires, are not effective for deforming MPIT wires, and that as with prior studies of MPIT Bi2Sr2Ca2Cu3Oy conductors, hot extrusion is required for obtaining a multifilamentary structure with fine filaments. As a result, the Bi2212 MPIT wires reported here have low engineering critical current density. Nonetheless, by focusing on sections of wires that remain intact after deformation, it is also shown that the first heat treatment stage, the oxidation stage, plays a crucial role in chemical homogeneity, phase transformation, and microstructural evolution and three reaction pathways for MP oxidation are presented. Furthermore, it is found the Bi2212 grain alignment within an MPIT filament is significantly different from that found in OPIT filaments after PMP, indicating the formation of highly dense filaments containing Bi2212 fine grains and Ag particles before PMP aids the formation of large, c-axis textured Bi2212 filaments during PMP. These results show that, with improved wire deformation, high critical current density may be obtained via a MPIT process.

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First‐ and Second‐Generation High‐Temperature Superconductor Wires

Wesche¹

2015

Physical Properties of High‐Temperature Superconductors

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Influence of precursor calcination parameters on the critical current density of Bi-2212 superconductors

Cited by 5 publications

References 31 publications

High critical current density Bi₂Sr₂CaCu₂O_x/Ag wire containing oxide precursor synthesized from nano-oxides

High critical current density Bi₂Sr₂CaCu₂O_x/Ag wire containing oxide precursor synthesized from nano-oxides

Formation of Bi₂Sr₂CaCu₂O_x/Ag multifilamentary metallic precursor powder-in-tube wires

First‐ and Second‐Generation High‐Temperature Superconductor Wires

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Influence of precursor calcination parameters on the critical current density of Bi-2212 superconductors

Cited by 5 publications

References 31 publications

High critical current density Bi2Sr2CaCu2Ox/Ag wire containing oxide precursor synthesized from nano-oxides

High critical current density Bi2Sr2CaCu2Ox/Ag wire containing oxide precursor synthesized from nano-oxides

Formation of Bi2Sr2CaCu2Ox/Ag multifilamentary metallic precursor powder-in-tube wires

First‐ and Second‐Generation High‐Temperature Superconductor Wires

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Product

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High critical current density Bi₂Sr₂CaCu₂O_x/Ag wire containing oxide precursor synthesized from nano-oxides

High critical current density Bi₂Sr₂CaCu₂O_x/Ag wire containing oxide precursor synthesized from nano-oxides

Formation of Bi₂Sr₂CaCu₂O_x/Ag multifilamentary metallic precursor powder-in-tube wires