Ultrasound effects on cerium, praseodymium, and terbium oxides

Abstract The behavior of intermediate higher rare earth oxides, such as Pr 6 O 11 and Tb 4 O 7 , and Ce 1- x Pr x O 2 compounds as powders has been studied by a new experimental procedure. They have been subjected to ultrasound irradiation (20 kHz) during immersion in a 5% dilute acetic acid solution. Pure PrO 2 and TbO 2 oxides (yield 100%) can be formed within sonication periods of 7-8 and 15-24 hr, respectively (instead of 3 days and 1 month through classical methods). Electron microscopic images and granulometry measurements show that the grain size has decreased greatly after sonication. The results are discussed in terms of cavitation phenomena and of chemical species (H 2 , O 2 , HO 2 , OH, H 2 O 2 ,…) formed during sonolysis of water and acetic acid.