Coprecipitation method for producing superconducting oxides of h

Details Coprecipitation method for producing superconducting oxides of h Coprecipitation method for producing superconducting oxides of h

1988-11-03

1990-01-23

Stoll, Robert L.

Superconductor technology: apparatus, material, process

High temperature , per se

Having tc greater than or equal to 150 k

423263, 423265, 423593, 423604, 501123, 501152, 502355, 502525, 252521, 505737, 505738, 505780, C01F 1102, C01F 1700, C01G 302

Patent

active

048958328

ABSTRACT:
A homogenous coprecipitation method by which superconducting oxides having perovskite-like structure, such as YBa2Cu307-x, can be produced in mass, in which urea is used as solvent to adjust and control the PH value of an aqueous nitrate solution. The coprecipitation method of this invention comprises following steps: (a) preparing an aqueous mixture containing Y, Ba and Cu salts with molar ratio of 1:2:3 wherein Y being 0.068M; (b) adding 5-10 moles of oxalic acid per one mole of Y and 20-250 moles of urea per moles of Y into the aqueous mixture; (c) heating the aqueous mixture to a temperature range of 80.degree. to 100.degree. C. to proceed a hydrolysis of the urea such that PH value of the aqueous mixture will be gradually elevated by NH.sub.3 gas evoluted from the urea hydrolysis; and (d) cooling the temperature of the aqueous mixture to room temperature at which time a desired uniform PH value is reached. After cooling, pale blue homogeneous coprecipitates of the superconducting oxides can be obtained.

REFERENCES:
Kawai et al., "Preparation of High-Tc Y-Ba-Cu-O Superconductor", Japanese Journal of Applied Physics, vol. 26, No. 5, May, 1987, pp. 1736-1737.
Liu et al., "Preparation of High Tc Superconducting Powders of Y.sub.1 B.sub.2 Cu.sub.3 O.sub.7-x by Homogeneous Coprecipitation", MRS, Apr. 1988.
Voigt et al., "A hydroxycarbonate Route to Superconductor Precursor Powders", Mat. Res. Soc. Symp. Proc., vol. 99, 1988, pp. 635-638.
Ye et al., "High-Tc Y:Ba:Cu:O Superconductors Synthesized By Various Pre-Solgel Techniques", MRS. Apr. 5, 1988.
Fujiki et al., "Preparation of a High-Tc Y-Ba-Cu-O Superconductor Using Colloidal Methods", Japanese Journal of Applied Physics, vol. 26, Jul. 1987, pp. 1159-1160.

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