Aluminium molybdate

Aluminium molybdate is the chemical compound Al₂(MoO₄)₃. It forms in certain hydrodesulfurization catalysts when alumina is doped with excess molybdenum. When molybdates are used to inhibit corrosion in aluminum piping, the protective film formed is hydrated aluminum molybdate. Although small quantities of aluminum molybdate form during aluminothermic reduction of molybdia, mechanical activation inhibits their formation.

Large-scale samples can be prepared via sol-gel synthesis, and have been proposed for molybdenum-99 storage in nuclear medicine.

The room temperature crystal structure was refined using time-of-flight powder neutron diffraction data. It is monoclinic and isostructural with Fe₂(MoO₄)₃ and Cr₂(MoO₄)₃. At high temperatures, the crystal rearranges to β‑Al₂(MoO₄)₃, isostructural with scandium tungstate.

Aluminum molybdate has a very low thermal expansion coefficient near room temperature.^{[citation needed]}