A novel synthetic method for the preparation of oxide superconductors: Anionic oxidation-reduction

Journal Article · Sun Oct 01 04:00:00 EDT 1989 · Journal of Solid State Chemistry; (USA)

DOI:https://doi.org/10.1016/0022-4596(89)90294-6· OSTI ID:7172051

Kourtakis, K; Robbins, M; Gallagher, P K ^[1]

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1. AT and T Bell Labs., Murray Hill, NJ (USA)

A new chemical method for the bulk synthesis of Ba{sub 2}YCu{sub 3}O{sub 7} powder is described and is applicable to the synthesis of other superconducting oxides. Ionic salt precursors are used which are intimately mixed by spray-drying an aqueous solution of these salts. The anions in the spray-dried mixtures (which in this study are mixtures of nitrate and acetate salts) participate in a low-temperature oxidation-reduction reaction. The exothermic redox reaction and the heat evolved from the reaction completely convert the precursors into their corresponding mixed oxides at temperatures below 300{degree}C in one reaction step. Phase segregation (normally apparent in the decomposition of organic precursors) is not observed in the decomposition of the mixed anion (nitrate/acetate) precursors. The enthalpy of this reaction is strongly dependent upon acetate content in the mixture: {minus}{Delta}H (9:4, acetate:nitrate) = 4016 (70) kJ/mole, whereas {minus}{Delta}H (5:8, acetate:nitrate) = 890 (70) kJ/mole. These precursors can be reacted at 910{degree}C for 10 min to produce single-phase Ba{sub 2}YCu{sub 3}O{sub x}. Sintered disks of Ba{sub 2}YCu{sub 3}O{sub 7}, prepared from Ba{sub 2}YCu{sub 3}O{sub x} powder, show onset T{sub c} of 94-95 K and are fully superconducting by 90.5-91 K.

• OSTI ID: 7172051
• Journal Information: Journal of Solid State Chemistry; (USA), Journal Name: Journal of Solid State Chemistry; (USA) Vol. 82:2; ISSN 0022-4596; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360000* -- Materials
360104 -- Metals & Alloys-- Physical Properties
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METALS
BARIUM
CHALCOGENIDES
CHEMICAL REACTIONS
COMPOSITE MATERIALS
COPPER COMPOUNDS
COPPER OXIDES
DATA
ELEMENTS
EXPERIMENTAL DATA
INFORMATION
MATERIALS
MEASURING INSTRUMENTS
MEASURING METHODS
METALS
NUMERICAL DATA
OXIDATION
OXIDES
OXYGEN COMPOUNDS
REDUCTION
SUPERCONDUCTING COMPOSITES
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
YTTRIUM