13C NMR Study of the Solution Chemistry of Barium Titanium Citrate Gels Prepared Using the Pechini Process

The chemistry of the initial precursor solutions of the barium titanate citrate gel prepared using the Pechini process was characterized by carbon nuclear magnetic resonance spectroscopy (¹³C NMR). Several experiments have been conducted to investigate the effect of the order of adding the species in the initial precursor solutions on synthesis of the barium titanium citrate gel. Based on the data from ¹³C NMR and photoacoustic Fourier-transform infrared spectroscopy (PA-FTIR) in previous work, it was found that the alcoholic and terminal carboxyl ligands of citric acid (CA) chelating with titanium ions are deprotonated. Esterification has a significant influence on the reaction of the species in the solution. Reaction mechanisms of the species in the precursor solution have been detailed. The possible molecular structures of Ti-CA and a barium titanate mixed-metal CA complex are proposed.