Antimony tetroxide is an inorganic compound with the formula Sb2O4. This material, which exists as the mineral stibiconite (also known as cervantite), is white but reversibly yellows upon heating. The material, with empirical formula SbO2, is called antimony tetroxide to signify the presence of two kinds of Sb centers.
The material is mixed valence, containing both Sb(V) and Sb(III) centers. Two polymorphs are known, one orthorhombic and one monoclinic. Both forms feature octahedral Sb(V) centers arranged in sheets with distorted Sb(III) centers bound to four oxides.