Scandium oxide

 ( Scandium Compounds ) 

Scandium(III) oxide or scandia is a inorganic compound with formula scandium₂oxygen₃. It is one of several of rare earth elements with a high melting point. 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 , and glass composition (as a helper material).

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Structure and physical properties Scandium(III) oxide adopts a cubic crystal structure (point group: tetrahedral (T_h), space group: Ia) containing 6-coordinate metal centres.Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications Powder diffraction analysis shows Sc−O bond distances of 2.159–2.071 Å.

Scandium oxide is an insulator with a band gap of 6.0 eV.

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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) and kolbeckite ScPO₄·2H₂O are rare, however trace amounts of scandium are present in many other minerals. Scandium oxide is therefore predominantly produced as a by-product from the extraction of other elements.

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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 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 H₂O

ScCl₃· 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.McCleverty, J.A. and Meyer, T.J., Comprehensive Coordination Chemistry II, 2003, Elsevier Science, , Vol. 3, p. 99 "Refluxing

Metallic scandium is produced industrially by the redox 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 (but like lutetium oxide), for example forming K₃Sc(OH)₆ with KOH. In this, scandium oxide shows more similarity with aluminium oxide.

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Natural occurrence Natural scandia, although impure, occurs as mineral kangite.Mindat, http://www.mindat.org/min-42879.html

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