Solvent Pechini method

The citrate method, also called polymerizable complex method, was first developed by Pechini [26], The process uses citric acid (CA) to chelate metal ions and ethylene glycol (EG) as a solvent for the polymerization to form an intermediate of polyester-type resin. According to Popa and Kakihana [27] the process consists of three major steps (i) complexation of metal ions with citric acid in water (ii) polymerization, where the formed chelates undergo polyesterification with ethylene glycol and (iii) decomposition of the organic network to obtain the powder precursor. These steps can be seen on Figure 4. 

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