Method of producing superconducting ceramics by co-precipitation of carbonates

A process for producing a homogeneous mixture of precipitated carbonate salts capable of reacting together in an oxygen atmosphere at an elevated temperature to form a superconducting ceramic which comprises:

• (a) forming a first solution by dissolving in a first solvent maintained at a temperature of from about 15.degree. to 35.degree. C. a rare earth compound, an alkaline earth metal compound, and a copper compound capable of reacting with a carbonate ion to form an insoluble precipitate of carbonate salts in the solvent used to form the solution;
• (b) forming a second solution containing a carbonate-forming compound selected from the class consisting of trihaloacetic acid, methyl acetoacetate, and ethyl N-methyl carbamate dissolved in a second solvent miscible with said first solvent;
• (c) adjusting the pH of said second solution to about 7.0;
• (d) blending said first and second solutions together at a temperature of from about 0.degree. to 15.degree. C. to inhibit formation of a precipitate;
• (e) adjusting the pH of said blend of solutions to about 5.5-6.0;
• and
• (f) heating said blended solutions to a temperature sufficient to cause said compound dissolved in said second solution to decompose to form said carbonate anion to form a carbonate precipitate comprising a homogeneous mixture of the carbonate salts of said rare earth, alkaline earth metal, and copper compounds dissolved in said first solution.

A process for producing a homogeneous mixture of co-precipitated carbonate salts consisting essentially of a mixture of rare earth carbonates, alkaline earth metal carbonates, and copper carbonates in a ratio sufficient to permit reacting the carbonate mixture together in an oxygen atmosphere at an elevated temperature to form a superconducting ceramic having the formula XY.sub.2 Cu.sub.3 O.sub.(6.5+a), wherein X is a rare earth element, Y is an alkaline earth metal, and a is greater than 0 and less than 0.5 which comprises:

• (a) forming a first solution by dissolving, in a first solvent maintained at a temperature of from about 15.degree. to 35.degree. C., a mixture of compounds, in a ratio of three rare earth atoms, two alkaline earth atoms and one copper atom, capable of reacting with a carbonate ion to form an insoluble co-precipitate of carbonate salts in the solvent used to form the solution, said mixture of compounds consisting essentially of:
• (1) a rare earth compound selected from the class consisting of nitrate, sulfate, halide, or organic salts of a rare earth;
• (2) an alkaline earth metal compound selected from the class consisting of nitrate, sulfate, halide, or organic of an alkaline earth metal;
• and
• (3) a copper compound selected from the class consisting of nitrate, sulfate, halide, or organic salts of copper;
• (b) forming a second solution by dissolving, in a second solvent miscible with said first solvent and also maintained at a temperature of from about 15.degree. to 35.degree. C., a carbonate-forming compound selected from the class consisting of trichloroacetic acid, tribromoacetic acid, and trifluoroacetic acid;
• (c) adjusting the pH of said second solution to about 7.0;
• (d) blending said first and second solutions together at a temperature of from about 0.degree. to 15.degree. C. to inhibit formation of a precipitate;
• (e) adjusting the pH of said blend of solutions to about 5.5-6.0;
• and
• (f) heating said blended solutions to a temperature of from about 50.degree. to 90.degree. C. while maintaining said pH at from about 5.5-6.0 and then, after reaching said temperature, adjusting the pH to about 7.0 to cause said carbonate-forming compound dissolved in said second solution to decompose to form said carbonate anion to form a carbonate precipitate comprising a homogeneous mixture of rare earth metal carbonates, alkaline earth metal carbonates, and copper carbonates in a stoichiometric ratio of three rare earth atoms per two alkaline earth metal atom per copper atom.

A process for producing a homogeneous mixture of materials capable of being subsequently formed into a superconducting ceramic which comprises:

• (a) forming a first solution by dissolving in a first solvent two or more compounds having cations capable of reacting with carbonate ions to form an insoluble precipitate of carbonate salts in the solvent used to form the solution;
• (b) forming a second solution consisting essentially of a second solvent miscible with said first solvent and a carbonate-forming compound dissolved therein capable of forming carbonate ions upon subsequent heating of the solution;
• (c) blending said first and second solutions together into a homogeneous mixture at a temperature sufficiently low to inhibit formation of said carbonate ions or a precipitate;
• and
• (d) heating said blended mixture sufficiently to form said carbonate ions resulting in formation of a carbonate precipitate comprising a homogeneous mixture of the carbonate salts of said cations in said compounds dissolved in said first solution.