Aqueous Solution-Gel Methods

Another route for the preparation of precursor solutions for CSD processed thin films is that based on the use of water as a solvent Metal reagents are mainly inorganic salts or water-soluble complexes of the metal with citric acid, hydrogen peroxide, or ethylenediaminetetraacetic acid. 

Different reactions can occur between a metal cation, M , and water, H2O  

2) Partial hydrolysis leads to polynuclear hydrolysis products and condensed species in water [30], which precipitate for most metal ions. The formation of these species occurs through four major reactions  

3) These partially hydrolyzed metal compounds can form metal complexes with a-hydroxycarboxylato and other electron-donating ligands (L), producing metal complexes soluble in water that are spinnable precursors with appropriate rheological properties for their deposition by CSD [31]. 

2 Chemical Solution Deposition of Electroceramk Thin Films 1853 

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Different strategies in the solution are described in the literature for the preparation of CSD precursors, where the prominence of the type of chemicals transcends the former grouping of solution methods. In general, but especially in the case of complex oxide compositions, neither of them can be used alone to obtain the liquid precursor due to difficulties in finding available metal reagents of the same family (e.g., alkoxides, carboxylates, and p-diketonates) for all the cations involved in the system. Therefore, a combination of several approaches is used to stabilize all the metal reagents in a common and stable solution. Some of these methods are shown here. They are divided considering the type of precursor used to obtain a stable solution, more than the traditional classification of solution methods shown above. Seven major solution processes are explained next alkoxide-based methods, carboxylate- and p-diketone-based methods, Pechini methods, diol routes, amine-based methods, polymer-assisted methods, and aqueous solution-gel methods. 

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