Compound metal oxides of a rare earth metal, an alkaline earth metal and copper of specific compositions have recently drawn attention as superconductor materials which exhibit superconductivity at temperatures higher than the boiling point of liquefied nitrogen. These materials are available only in the form of powder or sinter at present. Flexible superconductive materials are not yet known, but are desired today as materials for electromagnetic shielding, for preparing printed electric circuits in which small electric current flows, etc.
Superconductive compound metal oxides per se are known. Various processes have been proposed for preparing them.
Typical of these are:
(1) a process in which an oxide, a carbonate or an oxalate of the respective component metals are physically crushed and mixed in the state of powder, and the mixture is fired and pulverized;
(2) a process in which water-soluble salts such as nitrates, chlorides, etc. of the respective component metals are dissolved in water to make a homogeneous solution, the metals are coprecipitated as insoluble hydroxides, carbonates or oxalates by addition of hydroxide ions, carbonate ions or oxalate ions, and the coprecipitate is collected and fired into a compound metal oxide; and
(3) a rather recently developed process in which an organic solvent solution (strictly speaking, suspension) of organic compounds, especially alkoxides, of the component metals is hydrolyzed, and the resulting compound hydroxide is fired to give a compound metal oxide.
We tried to incorporate powder of superconductive compound metal oxide in resin (plastic) materials and accomplished in this invention.