Scandium oxide (CAS:12060-08-1)

Scandium(III) oxide, Sc2O3, or scandia, is a high melting rare earth oxide. It is used in the

preparation of other scandium compounds as well as in high-temperature systems (for its

resistance to heat and thermal shock), electronic ceramics, and glass composition (as a

helper material).

Structure and physical properties

Scandium(III) oxide adopts a cubic crystal structure (point group: tetrahedral (Th), space

group: Ia3) containing 6-coordinate metal centres. Powder diffraction analysis shows Sc-O

bond distances of 2.159-2.071Å. Scandium Oxide is an insulator with a band gap of 6.0 eV.

Production

Scandium oxide is the primary form of refined scandium produced by the mining industry.

Scandium-rich ores, such as thortveitite (Sc,Y)2(Si2O7) andkolbeckite ScPO4·2H2O are

rare, however trace amounts of scandium are present in many other minerals. Scandium

oxide is therefore predominately produced as a by-product from the extraction of other elements.

Reactions

Scandium oxide is the primary form of refined scandium produced by the mining industry,

making it the start point for all scandium chemistry.

Scandium oxide reacts with most acids upon heating, to produce the expected hydrated product.

For example, heating in excess aqueous HCl produces hydrated ScCl3·nH2O. This can be rendered

anhydrous by evaporation to dryness in the presence of NH4Cl, with the mixture then being purified

by removal of NH4Cl by sublimation at 300-500°C. The presence of NH4Cl is required, as the

hydrated ScCl3·nH2O would otherwise form a mixed oxychloride upon drying.

Sc2O3 + 6 HCl + x H2O → 2 ScCl3·nH2O + 3 H2OScCl3·nH2O + n NH4Cl → ScCl3 + n 

H2O + n NH4Cl

Likewise, it is converted into hydrated scandium(III) triflate (Sc(OTf)3·nH2O) by a reaction

with triflic acid.

Metallic scandium is produced industrially by the reduction of scandium oxide; this proceeds

via conversion to scandium fluoride followed by a reduction with metallic calcium. This process

is in some ways similar to the Kroll process for the production of metallic titanium.

Scandium oxide forms scandate salts with alkalis, unlike its higher homologues yttrium oxide and

 lanthanum oxide, for example forming K3Sc(OH)6 with KOH. In this, scandium shows more

similarity with aluminium oxide.