Influence of synthesis procedure on the morphology of bismuth oxide particles

摘要

A modified sol-gel procedure, based on the esterification reaction, was used to prepare the Bi_2O_3 precursor, which was then heated to 400 or 500℃. β-Bi_2O_3 obtained at 400℃ showed well-shaped plate-like particles. The mixture β-Bi_2O_3/α-Bi_2O_3, obtained by prolonged heating at 400℃, yielded pseudospherical particles having about 100 nm in size and much larger particles, as found by FE SEM. α-Bi_2O_3 obtained at 500℃ consisted of particles of varying shapes and sizes. Vitrification of α-Bi_2O_3 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(NO_3)_3 solution with tetrame-thylammonium hydroxide at pH ～ 14 was used. The precipitation at pH ～3.5 yielded cloverleaf-like particles of good uniformity, which were assigned to BiOOH (isomorphous with (La_(0.26)Bi_(0.24))Bi_(0.5)OOH. It was found that these particles were made up of much smaller primary BiOOH particles.