Growth Kinetics of Self-Assembled Indium Hydroxide and Oxide in Electrolytic Alkali Halide Solution

Introduction of a critical amount of different alkali halides in an otherwise identical aqueous synthesis condition was found to produce different morphologies of indium hydroxide from an In metal source. In this study, synthesis in KCl medium leads to polycrystalline bundled rodlike morphology whereas KI medium leads to a single-crystalline sheetlike morphology of indium hydroxide, which upon being annealed at 250 degrees C transforms to oriented mesocrystals of cubic and hexagonal indium oxide phases, respectively. The difference in the morphology is likely due to the change in the pressure at the interface of the solution and the product, which is controlled by the structure and interactions of the monomers, similar to that observed for block copolymers. The evolution of the polymorphs comes with some interesting thermodynamics of decomposition, which is evident in the thermal studies. This study also indicates the role of crystallinity and dimensionality of indium hydroxide in the formation of different polymorphs of indium oxide.