Verfahren zur Abscheidung von Titanoxid-Schichten unter Verwendung von loeslichen Pulvern

DE 19845291 A UPAB: 20000613 NOVELTY - A sol-gel method for preparing titanium oxide layers involves preparing a soluble powder (I) containing titanium, dissolving (I), coating a substrate with the obtained sol and tempering, where (I) is prepared by reacting a titanium alcoholate with a polar complexing and chelating agent, heating the solution, treating with water and concentrating. DETAILED DESCRIPTION - A sol-gel method for preparing titanium oxide layers involves preparing a soluble powder (I) containing titanium, dissolving the powder to form a sol, coating a substrate with the sol and tempering the coated substrate. Preparation of (I) is carried out by: (a) reacting a titanium alcoholate of formula Ti(OR)4 (II) with at least one polar compound (III) having complexing and chelating properties; (b) heating the solution; (c) treating the solution with water, optionally in presence of a catalyst; and (d) concentrating the solution. R = linear, branched or cyclic alkyl or alkenyl of 1-10C, optionally having one or more carbonyl, ester and/or carboxy functions. INDEPENDENT CLAIMS are included for: (i) a titanium-containing powder (I') for the deposition of titanium oxide layers, obtained by steps (a)-(d) as above except that the titanium alcoholate is not restricted to formula (II) and (ii) a coating solution for the preparation of titanium oxide layers, comprising a colloidal solution of (I') in an alcohol, diol, amine and/or water. USE - The method is specifically used for applying titanium oxide layers to substrates of glass (especially borate glass), ceramic and/or metal, particularly in tubular or flat form (all claimed). The use of (I') or its collodial solution is claimed in: (i) preparation of electrochromic imaging screens, optical reflection layers or photo-anodes; (ii) preparation of microstructured layers; or (iii) photocatalytic purification of waste waters. ADVANTAGE - The process allows TiO2 layers of relatively high thickness (e.g. above 150 nm) to be deposited in a single stage. The coatings can be applied to large areas of substrates of a wide range of materials and geometries. Drying of wet films before pyrolysis is unnecessary. The layers have good adhesion, even to borosilicate glass. The method can be used to prepare e.g. layers more than 0.4 mu m thick having a net-like fissure structure, finely structured layers (using additives such as polyethylene glycol) and/or layers doped with other materials such as transition or rare earth metals. (I)/(I') can be used to prepare solutions having a high TiO2 solids content, dissolve without residue formation in a wide range of solvents and can be stored in air indefinitely