Process for Non-agglomerated Nanometer-sized Barium Titanate Powders by Sol-gel Auto-igniting Synthesis

摘要

Non-agglomerated nano-sized BaTiO_3 powders were prepared by a 3 step decomposition of barium titanyl citric acid chelate derived from Ba(NO_3)_2-TiO(NO_3)_2-citric acid-NH_4NO_3 based complex compound system. The 1st step was the thermal treatment of chelate wet gel at 150℃ for 40min to remove water and non-bridging hydroxyl groups and to form expanded gel intermediate. The 2nd step was the decomposition of the organic fuel by igniting expanded gel intermediate at 300℃. The 3rd step was the formation of the high purity BaTiO_3 by calcining the decomposed powders at 700℃ for 2 hours. The most expanded gel intermediate was found to be a decisive factor for the elimination of hard agglomerate. In addition, the initial oxidant/fuel molar ratio was shown to strongly influence the characteristics of the powders thus obtained. The optimum oxidant/fuel value was 3 for obtaining non-agglomerated pure BaTiO_3 powders with a particle size of 50 nm. The agglomerate degree of BaTiO_3 powders was determined by particle morphology and uniformity of the green compact microstructure observed by field emission scanning electron microscopy and scanning electron microscope.