The Formation of Monodispersed Indium(III) Hydroxide Particles by Forced Hydrolysis at Elevated Temperature

Rather poorly crystallized spherical particles of indium(III) hydroxide were produced by forced hydrolysis at 100°C for 120 min under the conditions of 6.0×10−4 mol dm−3 for indium(III) ions, 1.0×10−3 mol dm−3 for nitric acid, and 1.25 for a concentration ratio, [SO42−]t/[In3+]t, respectively, having an average size of 0.48 μm with a relative standard deviation of 0.09. On the other hand, cubic particles of well-crystallized indium(III) hydroxide were yielded in a nitrate solution that was free from sulfate ions and at the same concentrations. The cubic particles grew through a polynuclear layers mechanism. Monomeric hydroxo complexes basically acted as precursors of the spherical particles, together partly with polymeric ones. The point of zero charge was estimated as being at the same pH (7.7) for both the hydroxide and oxide particles prepared from the nitrate system, in contrast to those of 7.0 and 5.4 for the respective particles obtained from the sulfate system.