Abstract: Metal oxide superconductors of the yttrium-barium-copper type can be formed by precipitation from an aqueous solution of the salts of the metals using an oxalate precipitation reagent under basic pH conditions to form a fireable precursor only partly in the form of the oxalate salts of these metals.

Abstract: A now superconducting material comprising a compound oxide represented by the general formula:(Ba, .gamma.)x(.alpha.,.beta.).sub.1-x .epsilon..sub.y Cu.sub.1-y O.sub.3-zin which".gamma." represents an element of IIa group of the periodic table except Ba, an atomic ratio of .gamma. to Ba being selected in a range between 1% and 90%,".alpha." represents Y or La,".beta." represents an element of IIIa group of the periodic but is different from .alpha., an atomic ratio of .beta. to .alpha. is selected in a range between 1% and 90%,".epsilon." represents a metal element of IIIb group of the periodic table,x, y and z are numbers each satisfies ranges of 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, and 0.ltoreq.z<1 respectively, andthe expression of (Ba, .gamma.) and (.alpha.,.beta.) mean that the respective elements position predetermined sites in a crystal in a predetermined proportion.