Hoechst Aktiengesellschaft

Winfried Becker

Leonhard Walz

Hans-Georg Von Schnering

Martin Schwarz

Martin Hartweg

Christoph Lang

Bernhard Hettich

Stephan Weidlich

Carsten Budesheim

Thomas Popp

Elfi Waldschmidt

Joachim Adam

A description is given of superconducting substances having a content of Bi, Sr, Ca and Cu, and of processes for their preparation from the metal oxides within a range which is specified by the overall composition Bi.sub.a (Sr,Ca).sub.b -Cu.sub.6 O.sub.x, where a=3-24 and b=3.23-24, with an Sr/Ca atomic ratio of 1:9-9:1 and a Bi:(Ca+Sr) atomic ratio of 0.3-1.5. The transition temperature is at least 60 K. The principal phase crystallizes in the orthorhombic system. The pure compounds Bi.sub.4 (Sr,Ca).sub.4 Cu.sub.2 O.apprxeq..sub.12 and Bi.sub.4 (Sr,Ca).sub.6 Cu.sub.4 O.apprxeq..sub.20.

Process for making high temperature Bi-Sr-Ca-Cu oxide superconductor

To prepare a phase-pure, ceramic oxide superconductor which contains, in addition to copper, at least one alkaline earth metal from the group comprising Ba, Sr and Ca, and at least one metal from the group comprising Y, La, Tl, Pb and the rare earths, for example of YBa.sub.2 Cu.sub.3 O.sub.7-x, a solution is prepared which contains the metal components in the atomic ratios of the superconductor. The metals are precipitated as oxalates by combining this solution with an oxalic acid solution, the mixture of the oxalates is separated off, dried and decomposed to form the oxides, and the latter are subsequently sintered at temperatures of from 700.degree. to 900.degree. C. in the presence of oxygen to form the superconductor. In this process, the heating of the metal oxalates and the oxides formed therefrom up to 700.degree. C. is carried out at a maximum oxygen partial pressure of 50 mbar, preferably in an inert gas.

Process for the preparation of a semiconductor from an oxalate

Molding of sintered strontium/calcium indate and the use thereof

An alkaline earth metal chelate complex of 2,2,6,6-tetramethylheptanedione of the formula (I)

Volatile alkaline earth metal complex and its use

The invention relates to a process for producing a bismuth-, copper-, strontium- and calcium-containing high-temperature superconductor, in which an aqueous solution is produced which has a pH of 0.5-4 and which contains the metals in an atomic ratio corresponding to a high-temperature superconductor, the solution is combined with an oxalic acid solution to precipitate the metals quantitatively as oxalates, the oxalates formed are separated off and decomposed thermally to form the oxides and the latter are reacted in the presence of oxygen at temperatures above 700.degree. C. to form the desired high-temperature superconductor. The process comprises concentrating the aqueous solution of the metal until a precipitate begins to appear and using the oxalic acid as a solution in an organic solvent which is miscible with water The oxalates are decomposed at 550-700.degree. C. in the presence of oxygen.

Process for producing a high-temperature superconductor containing

Solutions containing the cations of the metals Y, Ba, Cu in the atomic ratio 1:2:3 or the cations of the metals Bi, Sr, Ca and Cu having the atomic ratios of a high-temperature superconductor bound to polyacrylic acid in water as dispersant and having a viscosity of 150-10,000 cSt (at 20.degree. C.) serve to produce superconducting filaments or coatings. To produce a superconducting filament, a solution is forced through a nozzle and the extruded filamentous strand is left to solidify in an organic solvent which is miscible with water, the filament is isolated, dried and heated to at least 800.degree. C. in the presence of oxygen, annealed at at least 800.degree. C. for at least one hour in the presence of oxygen and then cooled.

Solution and its use to produce superconducting filaments and coatings

Multiphase superconductor and process for its production

Black crystal compositions having the empirical composition Bi.sub.a Sr.sub.b Cu.sub.c O.sub.d are described where a+b+c=1, A=0.36-0.557, b=0.098-0.496, c=0.1-0.4 and d=approximately 1+a/2. These compositions have a superconducting transition temperature T.sub.c for superconductivity of greater than 20 K and contain a principal phase which crystallizes in the orthorhombic system. They can be prepared from the mixture of the oxides in the atomic ratio stated by heating to 700.degree.-1000.degree. C.

Growing community of inventors

Kelkheim, Germany

Winfried Becker