NOVELTY - Manufacture of electrochemical device (I) (including a cathode, anode and electrolyte membrane, each containing ceramic materials) comprises thermally treating a solution comprising metal cation, hydrosoluble monomer with an ester moiety and cross-linking monomer with ethylenically unsaturated ester moiety to provide a gel and metal cation in oxide form; calcining the gel to form nanosize powder; and sintering the powder to form ceramic material.    USE - The invention deals with the manufacturing of an electrochemical device that is a solid oxide fuel cell.    ADVANTAGE - (I) has reliable and efficient performance, and provides cathode, anode and/or electrolyte membrane based on ceramics prepared from nanosize powders. The process for producing nanosize powder allows large scale production of substantially pure and homogeneous powders in high yields. The in situ formation of a gel from a hydrosoluble ethylenically unsaturated ester monomer and a cross-linker eliminates the problem of metal cation interaction, and allows large scale obtainment of nanosize chemically complex products in a single batch (without the necessity of employing chelating agents).    DETAILED DESCRIPTION - Process for manufacturing an electrochemical device (including a cathode (A), an anode (B) and at least one electrolyte membrane (C) disposed between (A) and (B); where each contains at least a ceramic material (D)) comprises: (1) 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; (2) calcining the gel to remove organic substances and to form a crystal phase of at least one metal oxide in a nanosize powder form; and (3) sintering the powder to provide the ceramic material. An INDEPENDENT CLAIM is also included for the process of manufacturing a nanosize oxide powder.