Properties and Overview of Tellurium

Overview:

Tellurium (Te) with the chemical symbol Te and atomic number 52, is a metalloid with properties shared by both metals and non-metals. It was discovered in 1782 by Austrian mineralogist Franz-Joseph Müller von Reichenstein, who initially confused it with antimony. Tellurium is named after the Latin word "tellus," meaning "earth," reflecting its terrestrial origins. Physically, tellurium is a brittle, silvery-white element with a metallic luster. It is a semiconductor, meaning it can conduct electricity better than an insulator but not as well as a metal. This property becomes more pronounced at higher temperatures. Tellurium has a melting point of 449.5°C and a boiling point of 988°C. It has a density of 6.24g/cm³, placing it in the mid-range of density among the elements. In its crystalline form, tellurium exists as long, needle-like crystals, while in its amorphous form, it appears as a dark, powdery substance.
Chemically, tellurium exhibits properties characteristic of metalloids and chalcogens, a group it belongs to alongside oxygen, sulfur, selenium, and polonium. It commonly forms compounds in oxidation states of -2, +4, and +6. In its most stable form, tellurium combines with metals to form tellurides, which are compounds where tellurium carries a -2 oxidation state. Tellurium also forms oxides, such as tellurium dioxide (TeO₂), and halides, such as tellurium tetrachloride (TeCl₄). It has a moderate reactivity, burning in air to form tellurium dioxide and reacting with halogens to form halides. However, it is less reactive than sulfur or selenium.
Regarding safety, tellurium and its compounds should be handled carefully, as they can be toxic if ingested or inhaled. Exposure to tellurium, even in small amounts, can lead to tellurium breath, a condition characterized by a garlic-like odor on the breath caused by the body's metabolism of tellurium into dimethyl telluride. Tellurium compounds, particularly in their more reactive forms, can cause skin and eye irritation, and inhalation of tellurium dust can lead to respiratory problems. Due to these risks, proper protective equipment, such as gloves and masks, should be used when handling tellurium and its compounds.

Production:

Tellurium is typically produced as a byproduct of copper refining. It is found in the Earth's crust in association with gold and other metals, often in the form of tellurides. The extraction of tellurium begins with the anode slimes collected during the electrolytic refining of copper. These slimes contain small amounts of tellurium, which is then separated through a series of chemical reactions, including oxidation and reduction processes, to isolate the element. Tellurium is also recovered from lead and bismuth ores, although these sources are rare.

Applications:

Tellurium has a range of essential applications, particularly in the electronics and metallurgy industries. One of its most significant uses is in producing cadmium telluride (CdTe) photovoltaic cells used in solar panels. Cadmium telluride is an efficient semiconductor material for converting sunlight into electricity, and it is valued for its cost-effectiveness in large-scale solar power generation. In electronics, tellurium is used to improve the properties of semiconductors and as an alloying agent in steel and copper, enhancing their machinability and strength. It is also used in thermoelectric devices, where it helps convert heat into electrical energy or vice versa.
Additionally, tellurium is employed to produce certain types of glass, improving optical properties and thermal shock resistance. In the rubber industry, tellurium compounds are used as vulcanizing agents, which help cross-link polymer chains to make rubber more durable and elastic. Tellurium's role in the chemical industry includes its use as a catalyst in synthetic organic reactions and refining petroleum products.

Summary:

Tellurium is a versatile metalloid with distinct physical properties, such as brittleness and semiconductor behavior. Chemically, it forms various compounds with metals and non-metals, exhibiting multiple oxidation states. Tellurium is primarily produced as a byproduct of copper refining and is used in various applications, from solar cells to electronics and metallurgy. While generally stable, tellurium and its compounds require careful handling due to their toxicity. Its unique combination of properties makes it valuable in advanced technology and industrial processes.

See a comprehensive list of atomic, electrical, mechanical, physical and thermal properties for tellurium below: