NOVELTY - Preparing polymerised inorganic-organic precursor solution involves forming a solution of at least one metal cation and at least one organic compound and heating the solution to a temperature of 20-300 degrees C to form a polymerised inorganic-organic solution of precursor for nano-sized metal oxides, and concluding the heating when the room temperature viscosity of the solution is 10-500 mPa.s.    USE - For preparing polymerised inorganic-organic precursor solution for nano-sized metal oxides; and in stack for gas separation, power generation and oxygen separation (claimed). The polymerised inorganic-organic precursor solution also useful as dispersants and as sintering aids for in reversible solid oxide fuel cell/solid oxide electrolyser cell.    ADVANTAGE - The polymerised inorganic-organic precursor solution has very large surface area compared to materials that are not nano-sized and thus has a higher driving force for sintering, by increasing the sintering activity. Each inorganic-organic polymer precursor in presence of polymeric backbones allows the even distribution of these precursors on the surface of each ceramic oxide particle. The polymerised inorganic-organic precursor solution effective as scavengers of impurities and shows improved ability to immobilize the impurities by reacting with it.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for following:    (1) preparing sintered membrane involving mixing the polymerised inorganic-organic precursor solution with a ceramic oxide powder, a solvent and optionally at least one polymeric compound to form a mixture, ball-milling the mixture to obtain a suspension, shaping the suspension, sintering the shaped suspension to obtain a sintered membrane;    (2) solid oxide fuel cell, solid oxide electrolyser cell or solid oxide membrane cell comprising the sintered membrane;    (3) stack comprising at least two solid oxide fuel cells, at least two solid oxide electrolyser cells or at least two solid oxide membrane cells.