Tellurium dioxide

Chemical Properties

Heavy, white, crystalline powder; odorless. Soluble in concentrated acids, alkalies; slightly soluble in dilute acids, water.

Physical properties

White crystals; dimorphic; exists in tetragonal and orthorhombic forms; density 5.75 g/cm³ (tetragonal), 6.04 g/cm³ (orthorhombic); melts at 733°C forming a deep yellow liquid; vaporizes at 1,245°C; insoluble in water; soluble in acids and alkalies.

Uses

TeO₂ can be potentially used in medical imaging and industrial monitoring processes.

Uses

Tellurium dioxide is also used in devices which can convert light into sound (acousto-optic material). Glasses made of tellurium oxide have high refractive indices and transmit into mid-IR region. It is used to make glasses with special properties. It is useful in optical waveguides and optical fiber amplification.

Uses

Tellurium dioxide is used to prepare tellurium metal, telluric acid, and many tellurium salts. It may also be used in the preparation of Ag2Te nanoparticles.

Production Methods

Tellurium dioxide in its orthorhombic form occurs in nature as mineral tellurite. It is mined from natural deposits. Also, tellurium dioxide is produced as an intermediate during recovery of tellurium metal from anode slimes of electrolytic copper refining (See Tellurium, Production). The dioxide also is prepared by treating tellurium metal with hot nitric acid to form 2TeO²HNO³. The product then is heated to drive off nitric acid.

General Description

Tellurium dioxide (TeO₂) is a ceramic material that can be used as a semiconducting oxide. It has a wide band gap and high mobility as determined by density functional theory (DFT) calculations. In bulk quantity, it exists in two polymorphs which include tetragonal α-TeO₂ and orthorhombic β-TeO₂.

Flammability and Explosibility

Non flammable

Safety Profile

Poison by intratracheal route. An experimental teratogen. Experimental reproductive effects. When heated to decomposition it emits toxic fumes of Te. See also TELLURIUM COMPOUNDS.

Purification Methods

Dissolve it in 5M NaOH, filter it and precipitate it by adding 10M HNO3 to the filtrate until the solution is acid to phenolphthalein. After decanting the supernatant, the precipitate is washed five times with distilled water, then dried for 24hours at 110o [Horner & Leonhard J Am Chem Soc 74 3694 1952].