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An improved technique for the fabrication of thallium-based superconducting oxides, and particularly Tl:Ba:Ca:Cu:O 2223 oxides, is described which allows production of very pure superconductors (>95% 2223 phase) having excellent structural characteristics. The method of the invention involves first forming a self-sustaining body of starting oxides and subjecting this body to a sintering technique wherein the temperature of the body is gradually raised to a maximum level of about 850°-930° C, followed by maintaining the body at this temperature for a period of about 48 hours. The body is then slowly cooled to avoid distortion and loss of superconducting character. Most preferably, the sintering is a two-stage operation, where the body is first heated at a relatively low rate (e.g., 1°-10° C/min.) to a temperature of about 650°-750° C, followed by faster heating at a higher rate to achieve the maximum sintering temperature. Cooling is likewise staged, involving slow cooling at a rate of about 0.1°-5° C/min. until a temperature of about 600°-650° C is reached. The body is maintained at this temperature for about 5-20 hours. Final cooling is allowed to occur naturally down to ambient temperature.



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Midwest Superconductivity, Inc. (Lawrence, KS); University of Arkansas (Fayetteville, AR)


Ying Xin, Department of Physics, University of Arkansas, Fayetteville, AR
Zhengzhi Sheng, Department of Physics, University of Arkansas, Fayetteville, AR
Yufang Li, Department of Physics, University of Arkansas, Fayetteville, AR