Abstract: Mixed oxides of zirconium and yttrium [ZrO.sub.2 (Y.sub.2 O.sub.3)], with an yttrium content (as computed as elemental metal) comprised within the range of from about 15 to about 21% by weight, as spherical particles with size comprised within the range of from 0.1 to 2 .mu.m, with an average size of the particles lower than 1 .mu.m, in the cubic crystal form, are obtained by:preparing a mixture by starting from an aqueous solution of zirconium and yttrium carboxylates; an organic solvent selected from the group consisting of nitriles or alcohols; and a non-ionic surfactant;causing solid colloidal particles of the precursor of mixed zirconium/yttrium oxides to precipitate from said mixture, by operating at a pH value comprised within the range of from 5 to 7, at room temperature or at temperature close to room temperature; andcalcining said precipitate of solid particles at a high temperature to cause said solid particles to be directly converted from the amorphous state into the cubic crystal form.

Abstract: A solid polymeric electrolyte is constituted by a solid solution of an ionic compound in an organic matrix of polyether nature, constituted by a mixture consisting of:a high-molecular-weight poly-(ethylene oxide); andthe product of polymerization of a vinylether having the formula:R--(O--CH.sub.2 --CH.sub.2).sub.n --O--CH.dbd.CH.sub.2wherein:R means the methyl or ethyl radical; andn is an integer within the range of from 2 to 6,with said polyvinylether having a number average molecular weight within the range of from about 1,000 to about 10,000 and the weight ratio of said poly(ethylene oxide) to said polyvinylether being within the range of from 10:90 to 90:10.