Iron is present in the form of iron(III) oxide in almost all natural sources of water. It is the most common supplement of iron for algae. It is a highly stable n-type semiconductor, and possesses a band gap of 2.0 to 2.2eV. It is widely used in solar photoelectrolysis cells. Self-organized nanoporous iron(III) oxide (haematite) has been prepared. Orientation effects on nearly opaque single crystals of iron(III) oxide have been investigated by laser Raman spectroscopy.
Iron(III) oxide may be used in the preparation of iron(III) oxide-hydrate gels.