Tantalum pentoxide
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IUPAC name
Tantalum(V) oxide
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Systematic IUPAC name
Ditantalum pentaoxide
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| Identifiers | |
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3D model (Jmol)
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| ChemSpider | |
| ECHA InfoCard | 100.013.854 |
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PubChem CID
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| Properties | |
| Ta2O5 | |
| Molar mass | 441.893 g/mol |
| Appearance | white, odorless powder |
| Density | β-Ta2O5 = 8.18 g/cm3 α-Ta2O5 = 8.37 g/cm3 |
| Melting point | 1,872 °C (3,402 °F; 2,145 K) |
| negligible | |
| Solubility | insoluble in organic solvents and most mineral acids, reacts with HF |
| Band gap | 3.8 - 5.3 eV |
| −32.0·10−6 cm3/mol | |
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Refractive index (nD)
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2.275 |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |
Tantalum pentoxide, also known as tantalum(V) oxide, is the inorganic compound with the formula Ta
2O
5. It is a white solid that is insoluble in all solvents but is attacked by strong bases and hydrofluoric acid. Ta
2O
5 is an inert material with a high refractive index and low absorption (i.e. colourless), which makes it useful for coatings. It is also extensively used in the production of capacitors, due to its high dielectric constant.
Tantalum occurs in the minerals tantalite and columbite (columbium being an archaic name for niobium), which occur in pegmatites, an igneous rock formation. Mixtures of columbite and tantalite are called coltan. Tantalite was discovered by Anders Gustaf Ekeberg at Ytterby, Sweden, and Kimoto, Finland. The minerals microlite and pyrochlore contain approximately 70% and 10% Ta, respectively.
Tantalum ores often contain significant amounts of niobium, which is itself a valuable metal. As such, both metals are extracted so that they may be sold. The overall process is one of hydrometallurgy and begins with a leaching step; in which the ore is treated with hydrofluoric acid and sulfuric acid to produce water-soluble hydrogen fluorides, such as the heptafluorotantalate. This allows the metals to be separated from the various non-metallic impurities in the rock.
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