Influence of synthesis procedure on the morphology of bismuth oxide particles

A modified sol-gel procedure, based on the esterification reaction, was used to prepare the Bi2O3 precursor, which was then heated to 400 or 500 degrees C. beta-Bi2O3 obtained at 400 degrees C showed well-shaped plate-like particles. The mixture beta-Bi2O3/alpha-Bi2O3, obtained by prolonged heating at 400 degrees C, yielded pseudospherical particles having about 100 nm in size and much larger particles, as found by FE SEM. alpha-Bi2O3 obtained at 500 degrees C consisted of particles of varying shapes and sizes. Vitrification of alpha-Bi2O3 was also observed. XRD showed a small fraction of unidentified phase(s) in these samples. Different microstructures were obtained when the precipitation from aqueous Bi(NO3)(3) solution with tetramethylammonium hydroxide at pH similar to 14 was used. The precipitation at pH similar to 3.5 yielded cloverleaf-like particles of good uniformity, which were assigned to BiOOH (isomorphous with (La0.26Bi0.24)Bi0.5OOH. It was found that these particles were made up of much smaller primary BiOOH particles. (c) 2006 Elsevier B.V. All rights reserved.