Process for making 90° K. superconductors by impregnating cellulosic article with precursor solution

Claim 1

An improved process for preparing a shaped article of a superconducting composition having the formula MBa 2 Cu 3 O x wherein M is selected from the group consisting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu; x is from about 6.5 to about 7.0; said composition having a superconducting transition temperature of about 90 K.; said process consisting essentially of (a) forming in acetic acid a mixture of M(C 2 H 3 O 2 ) 3 , barium acetate and copper acetate in an atomic ratio of M:Ba:Cu of about 1:2:3; (b) heating the resulting mixture to boiling, and adding sufficient formic acid to dissolve any undissolved starting material while continuing to boil the solution; (c) contacting an article of cellulose material with the solution from step (b), thereby impregnating the article with the solution, said article having the shape desired; (d) removing excess solution from the resulting impregnated article of cellulose material and drying the impregnated article; (e) heating the impregnated article of cellulose material to a temperature from about 850° C. to about 925° C. in an oxygen-containing atmosphere for a time sufficient to form MBa 2 Cu 3 O y , where y is from about 6.0 to about 6.4, said heating effecting carbonization of the cellulose material and oxidization of carbon without ignition; and (f) maintaining the resulting article in an oxygen-containing atmosphere while cooling for a time sufficient to obtained the desired product.