TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preparation (claimed): Preparation of the nanosize oxide powder comprises: thermally treating an aqueous solution comprising at least one metal cation, at least one hydrosoluble ethylenically unsaturated monomer with an ester moiety and a hydrosoluble cross-linking monomer with at least two ethylenically unsaturated ester moieties, to provide a gel and to obtain the metal cation in an oxide form; and calcining the gel to remove organic substances and to form a crystal phase of at least one metal oxide in a nanosize powder form. Preferred Components: (B) contains: a cermet material comprising a metallic portion (copper, aluminum, gold, praseodymium, ytterbium, cerium, nickel, iron, cobalt, molybdenum, platinum, iridium, ruthenium, rhodium, silver or palladium) and a ceramic portion (yttria-stabilized zirconia, ceria doped with gadolinia or samaria or La1-xSrxGa1-yMgyO3-delta, where x and y are 0-0.7 and delta is from stoichiometry); or a ceramic material (cerium oxide, manganese oxide, molybdenum oxide, titania, ceria doped with gadolinia or samaria, niobia-doped ceria, and perovskites). The electrolyte membrane contains a ceramic material (yttria-stabilized zirconia, ceria doped with gadolinia or samaria or La1-xSrxGa1-yMgyO3-delta, where x and y are 0-0.7 and delta is from stoichiometry). (A) contains oxides of rare earth elements and/or peroviskites optionally in combination with a doped ceria). The aqueous solution comprises water or water with at least one hydrosoluble solvent. The hydrosoluble solvent is alcohol, glycol, tetrahydrofuran or dioxane. The metal cation is lanthanum, strontium, chromium, zirconium, yttrium, aluminium, lithium, antimony, boron, cadmium, cerium, cobalt, copper, dysprosium, erbium, europium, gallium, gold, hafnium, holmium, iridium, iron, lutetium, manganese, molybdenum, nickel, niobium, osmium, palladium, platinum, praseodymium, rhenium, rhodium, rubidium, ruthenium, samarium, scandium, silver, sodium, tantalum, terbium, thorium, thulium, tin, titanium, tungsten, uranium, vanadium or ytterbium cations. The ethylenically unsaturated monomer is 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl phenacrylate, hydroxybutyl (meth)acrylate, butandiol monoacrylate, 2-(2-ethoxyethoxy)ethyl acrylate or dimethylamino ethyl (meth)acrylate. The cross-linking monomer is diacrylates (preferably polyethyleneglycol diacrylate) or triacrylates (preferably ethoxylated tromethylolpropanetriacrylate), where the acrylates groups are linked to alkoxylated moieties or polyoxialkylene linear units. The aqueous solution comprises a hydrosoluble polymerization initiator (preferably alpha, alpha'-azaisobutyronitrile, tetramethylene-ethylenediamine, hydrogen peroxide, benzoyl peroxide, dicumyl peroxide, ammonium, sodium or potassium persulfate). The hydrosoluble ethylenically unsaturated monomer is an ester compound (Ia) of formula ((R2)CH=C(R)-COOR1).R = H, 1-4C alkyl, aryl or aryl-(1-4C alkyl);R1 = 1-8C hydrocarbon group containing at least one polar group (COOH, NH2, NHRa, N(Ra) 2, OH, ORa, SO3H or SH);Ra = 1-6C alkyl (preferably 1-4C alkyl); andR2 = H, methyl, ethyl, propyl or phenyl.Preferred Process: At least one metal cation solution is obtained by dissolving a hydrosoluble precursor (oxides, chlorides, carbonates, beta-diketonates, hydroxides, nitrates, acetates and/or oxalates). The concentration of metal ion in the aqueous solution is higher than 0.5 (preferably 1-10) mol/l. The thermal treatment is effected at 50-150degreesC. The gel is dried at 80-300degreesC to obtain a xerogel before proceeding to the calcining step. The xerogel is disaggregated and subjected to the calcining step. The calcining step is carried out (at about 300-1500degreesC) by progressively increasing the temperature. The grinding step of the powder is carried out at an intermediate stage of the calcining step. The nanosize powder shows a mean primary grain size lower than 20 (preferably 3-15) nm. A reduction step is effected together with the sintering step and the reduction is effected under hydrogen atmosphere. The sintering of nanosize powder is preceded by a shaping step to shape the nanosize powder in the form of (A), (B) or (C) for (I).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (claimed): Preparation of the nanosize oxide powder comprises: thermally treating an aqueous solution comprising at least one metal cation, at least one hydrosoluble ethylenically unsaturated monomer with an ester moiety and a hydrosoluble cross-linking monomer with at least two ethylenically unsaturated ester moieties, to provide a gel and to obtain the metal cation in an oxide form; and calcining the gel to remove organic substances and to form a crystal phase of at least one metal oxide in a nanosize powder form. Preferred Components: (B) contains: a cermet material comprising a metallic portion (copper, aluminum, gold, praseodymium, ytterbium, cerium, nickel, iron, cobalt, molybdenum, platinum, iridium, ruthenium, rhodium, silver or palladium) and a ceramic portion (yttria-stabilized zirconia, ceria doped with gadolinia or samaria or La1-xSrxGa1-yMgyO3-delta, where x and y are 0-0.7 and delta is from stoichiometry); or a ceramic material (cerium oxide, manganese oxide, molybdenum oxide, titania, ceria doped with gadolinia or samaria, niobia-doped ceria, and perovskites). The electrolyte membrane contains a ceramic material (yttria-stabilized zirconia, ceria doped with gadolinia or samaria or La1-xSrxGa1-yMgyO3-delta, where x and y are 0-0.7 and delta is from stoichiometry). (A) contains oxides of rare earth elements and/or peroviskites optionally in combination with a doped ceria). The aqueous solution comprises water or water with at least one hydrosoluble solvent. The hydrosoluble solvent is alcohol, glycol, tetrahydrofuran or dioxane. The metal cation is lanthanum, strontium, chromium, zirconium, yttrium, aluminium, lithium, antimony, boron, cadmium, cerium, cobalt, copper, dysprosium, erbium, europium, gallium, gold, hafnium, holmium, iridium, iron, lutetium, manganese, molybdenum, nickel, niobium, osmium, palladium, platinum, praseodymium, rhenium, rhodium, rubidium, ruthenium, samarium, scandium, silver, sodium, tantalum, terbium, thorium, thulium, tin, titanium, tungsten, uranium, vanadium or ytterbium cations. The ethylenically unsaturated monomer is 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl phenacrylate, hydroxybutyl (meth)acrylate, butandiol monoacrylate, 2-(2-ethoxyethoxy)ethyl acrylate or dimethylamino ethyl (meth)acrylate. The cross-linking monomer is diacrylates (preferably polyethyleneglycol diacrylate) or triacrylates (preferably ethoxylated tromethylolpropanetriacrylate), where the acrylates groups are linked to alkoxylated moieties or polyoxialkylene linear units. The aqueous solution comprises a hydrosoluble polymerization initiator (preferably alpha, alpha'-azaisobutyronitrile, tetramethylene-ethylenediamine, hydrogen peroxide, benzoyl peroxide, dicumyl peroxide, ammonium, sodium or potassium persulfate). The hydrosoluble ethylenically unsaturated monomer is an ester compound (Ia) of formula ((R2)CH=C(R)-COOR1).R = H, 1-4C alkyl, aryl or aryl-(1-4C alkyl);R1 = 1-8C hydrocarbon group containing at least one polar group (COOH, NH2, NHRa, N(Ra) 2, OH, ORa, SO3H or SH);Ra = 1-6C alkyl (preferably 1-4C alkyl); andR2 = H, methyl, ethyl, propyl or phenyl.Preferred Process: At least one metal cation solution is obtained by dissolving a hydrosoluble precursor (oxides, chlorides, carbonates, beta-diketonates, hydroxides, nitrates, acetates and/or oxalates). The concentration of metal ion in the aqueous solution is higher than 0.5 (preferably 1-10) mol/l. The thermal treatment is effected at 50-150degreesC. The gel is dried at 80-300degreesC to obtain a xerogel before proceeding to the calcining step. The xerogel is disaggregated and subjected to the calcining step. The calcining step is carried out (at about 300-1500degreesC) by progressively increasing the temperature. The grinding step of the powder is carried out at an intermediate stage of the calcining step. The nanosize powder shows a mean primary grain size lower than 20 (preferably 3-15) nm. A reduction step is effected together with the sintering step and the reduction is effected under hydrogen atmosphere. The sintering of nanosize powder is preceded by a shaping step to shape the nanosize powder in the form of (A), (B) or (C) for (I). EXAMPLE - Hydrated cerium nitrate (Ce(NO3)3 6H2O; 1.8716 g) and hydrated gadolinium nitrate (Gd(NO3)3 6H2O; 0.4279 g) were added to water (10 ml), while stirring and heating up to 50degreesC to provide a solution with a metal cation concentration of 0.538 mol/l. 2-Hydroxyethylmethacrylate (10 ml) and polyethyleneglicoldiacrylate (5 ml) were added to the mixture. The solution was heated up to 100degreesC. Hydrogen peroxide (35 vol.%; 20 drops) was added to initiate the gel formation. The resulting gel was decomposed at 500degreesC for 5 hours to obtain cerium/gadolinium oxides nanopowder (1 g).