Effect of Particle Size in Raw Material CuO on Superconductivity of HTSC

Yoshizawa, Shuji; Yanagawa, Manabu; Haseyama, Shuetsu; Kawazu, Koichi; Itô, Yûichi

doi:10.1007/978-4-431-68141-0_62

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(2 citation statements)

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“…Here, starting with nano-size oxides, the phase transformation to Bi2212 is thorough and fast due to the substantially smaller particle size and larger surface area. Based on BET theory, the surface area is inversely proportional to particle size and small particle size increases greatly the reactivity and rate of phase transformations [21]. Furthermore, small particle size decreases phase segregation significantly in the as-made powders over a long length scale and thus repeated pulverizations and calcinations are not required to achieve high-purity Bi2212 precursors.…”

Section: Calcination and Phase Transformationsmentioning

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%

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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%

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

Zhang

Johnson

Naderi

et al. 2016

Supercond. Sci. Technol.

View full text Add to dashboard Cite

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Effect of Particle Size in Raw Material CuO on Superconductivity of HTSC

Cited by 1 publication

References 1 publication

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

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Effect of Particle Size in Raw Material CuO on Superconductivity of HTSC

Cited by 1 publication

References 1 publication

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

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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