Synthesis of barium titanate powders by aerosol pyrolysis of a Pechini-type precursor solution

Abstract

A Pechini-type precursor system, utilizing Ba-nitrate and Ti-isopropoxide with citric acid (CA) and ethylene glycol (EG), has been investigated for the synthesis of BaTiO₃ powders using aerosol pyrolysis. Powder produced at 350 °C in the aerosol process had subsequent thermal decomposition (TGA/DTA) behavior that was similar to that reported for the barium titanyl citrate complex BaTi(C₆H₆O₇)₃·xH₂O, indicating that the short process time and rapid droplet evaporation limit substantial polyester network development in the aerosol process. Crystalline phase development proceeded rapidly at reactor temperatures between 600 and 700 °C. Small amounts of the intermediate phases Ba₂Ti₂O₅CO₃, BaCO₃ and Ba(NO₃)₂,were present as impurities in powder produced at 700 °C, and phase-pure BaTiO₃ was produced at temperatures above 800 °C. In contrast, a precursor solution utilizing acetic acid as peptizing agent led to a significant amount of nonstoichiometric BaTi₂O₅, highlighting the importance of the multidentate complexation of citric acid. Dimpled or slightly collapsed hollow particles were typically produced using the Pechini-type precursor. It was demonstrated that the polymeric additives polyethylene glycol and methylcellulose could be used to alter particle morphology without impacting product phase-purity.