Industrial Technology Research Institute

Der-Shiuh Shy

Ru-Shi Liu

Chung-Ho Tai

Sheng-Feng Wu

Hui-Wen Lee

A family of mercury-containing Sr-(Ca.cndot.Y)-Cu-O superconducting materials having a zero-resistance temperature, T.sub.c(zero), greater than 90 K so that they can be cooled to and maintain the desired superconducting characteristics using relatively less expensive liquid nitrogen, are disclosed. The high-temperature superconductor is represented by the formula of: (Pb.sub.0.5 Hg.sub.0.5)(Sr.sub.2-x Ba.sub.x)(Ca.sub.0.7 Y.sub.0.3)Cu.sub.2 O.sub.7-.delta. ; wherein the value of x ranges between about 0.1 and about 0.6, preferably between about 0.2 and about 0.3. These superconducting materials are prepared by first grinding and mixing in open air constituent oxide powders of PbO, HgO, SrO.sub.2, BaO.sub.2, CaO, Y.sub.2 O.sub.3, and CuO. After mixing, the powder mixture is pressed under a pressure of about 5 ton/cm.sup.2 to form a pellet having a diameter of 8 mm and a thickness of 3 mm. Thereafter, the pressed pellet is wrapped with a gold foil (with a thickness of 0.05 mm), and sealed inside a quartz tube under vacuum (.about.10.sup.-4 Torr). The quartz tube containing the pellet was then placed inside a high temperature oven and sintered at 970.degree. C. for 24 hours.

Superconductor with 1212 phase of Hg,Pb,Sr,Ba,Ca,Y,Cu oxide

A process for fabricating Thallium-based superconducting tapes comprising the steps of: (1) preparing a powder mixture having a nominal composition of (Tl.sub.1-x-y Bi.sub.y Pb.sub.z)(Ba.sub.2-z Sr.sub.z)Ca.sub.2 Cu.sub.3 O.sub.9 ; (2) placing the powder mixture into a silver tube and drawing and/or swaging the silver tube containing the powder mixture into a wire having a pre-determined diameter, wherein x and y are real numbers between 0.2 and 0.4, and z is a real number between 0 and 2; (3) rolling the wire into a tape having a pre-determined thickness; and (4) subjecting the tape to a two-stage single-sintering process at two respective sintering temperatures. The two-stage single-sintering process of the present invention allows Thallium-based superconducting tapes to be fabricated which exhibit substantially increased critical current density, without causing a substantially increased cost and complexity, as do other prior art processes, such as the double-sintering process.

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Hsinchu, Taiwan

Der-Shiuh Shy