Aluminium Oxide
Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula Al2O3. It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium oxide. It is commonly called alumina and may also be called aloxide, aloxite, or alundum in various forms and applications. It occurs naturally in its crystalline polymorphic phase α-Al2O3 as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire. Al2O3 is significant in its use to produce aluminium metal, as an abrasive owing to its hardness, and as a refractory material owing to its high melting point.
Application
Corundum is the most common naturally occurring crystalline form of aluminium oxide. Rubies and sapphires are gem-quality forms of corundum, which owe their characteristic colours to trace impurities. Rubies are given their characteristic deep red colour and their laser qualities by traces of chromium. Sapphires come in different colours given by various other impurities, such as iron and titanium. An extremely rare δ form occurs as the mineral deltalumite.
| Chemical formula | Al2O3 |
|---|---|
| Molar mass | 101.960 g·mol−1 |
| Appearance | white solid |
| Odor | odorless |
| Density | 3.987 g/cm3 |
| Melting point | 2,072 °C (3,762 °F; 2,345 K) |
| Boiling point | 2,977 °C (5,391 °F; 3,250 K) |
| Solubility in water | insoluble |
| Solubility | insoluble in all solvents |
| log P | 0.31860 |
| Magnetic susceptibility (χ) | −37.0×10−6 cm3/mol |
| Thermal conductivity | 30 W·m−1·K−1 |
| Refractive index (nD) | nω = 1.768–1.772 |
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