Al2O3AlOH3

Al2O3AlOH3 is a condensed chemical notation used in materials science and mineralogy to denote a mixed aluminum oxide–hydroxide composition. It is not a single, well-defined compound, but a shorthand for phases in which oxide (Al2O3) and hydroxide (Al(OH)3) units coexist. The representation often appears in discussions of aluminum oxide hydrate systems, gels, precipitates, and precursors to alumina ceramics, where dehydration or hydrolysis shifts the balance between oxide-like and hydroxide-like components.

In these materials, aluminum centers are typically coordinated by oxygen and hydroxide ligands, forming networks that can be amorphous or poorly crystalline. The exact arrangement and proportion of oxide versus hydroxide groups vary with synthesis conditions, aging, and thermal treatment. The phase is closely related to known compounds such as gibbsite (Al(OH)3) and boehmite (AlO(OH)) and can be viewed as a non-stoichiometric mixture that bridges these end-states.

Synthesis and occurrence: Al2O3AlOH3-type compositions can arise by the hydrolysis or partial hydration of aluminum salts, by precipitation from alkaline solutions, or during the aging of alumina gels. Calcination removes hydroxyl groups and converts the material toward crystalline Al2O3, while partial dehydration yields oxide–hydroxide species with varying properties.

Applications: Materials with oxide–hydroxide character are used as precursors to alumina ceramics, catalyst supports, and adsorbents. Their porosity, surface area, and acidity depend on the degree of hydration and the presence of surface hydroxyl groups, influencing processing and performance.

See also: aluminum oxide, aluminum hydroxide, boehmite, gibbsite, diaspore, alumina hydrate.