Tellur
History
It was discovered in 1782 by the Austrian chemist and mineralogist Franz Joseph Müller von Reichenstein, who initially considered it to be "sulfured bismuth." It wasn't until 1797 that the Berlin chemist Martin Heinrich Klaproth could verify the discovery. Klaproth was a luminary, a man who also discovered uranium, zirconium, and cerium, and he named the resource discovered by Müller von Reichenstein "tellurium." The name Tellurium is derived from the Latin word for "earth."
Properties
The electrical conductivity, like in all semiconductors, can be increased by raising the temperature or by exposure to light. However, in tellurium, this leads to only a slight increase. The electrical conductivity and thermal conductivity of tellurium are anisotropic, meaning they depend on direction. Crystalline tellurium is a soft (Mohs hardness 2.25) and brittle material, which can be easily processed into powder. Increasing the pressure transforms tellurium into other crystalline modifications. Above 450 °C, tellurium transitions into a red melt.
| Properties | Value |
|---|---|
Melting Point | 449,5 °C |
Boiling Point | 989,8°C |
Specific Weight | 6,25g/cm³ |
Mass fraction/Earth's crust | 0,001 ppm |
Color | silver white |
Annual Production | ca. 180 t |
Main Producers | Kanada, Japan, Peru |
Usage | Alloys, solar cells, photodiodes, semiconductors, CDs/DVDs, vulcanization of rubber |
Applications
Tellurium is a versatile element. As an additive, it makes metal alloys more resistant to corrosion. Cadmium telluride is used in photovoltaics (thin-film solar cells). Tellurium is also found in coatings for submarine cables, in optical storage discs, and in specialty glasses for optical fibers. Additionally, tellurium is used in the vulcanization of rubber.
Prospects
Tellurium is a technically less significant element because its production is expensive and it can often be replaced by other elements or compounds. Elementary tellurium is used in the metal industry as an additive for steel, cast iron, copper and lead alloys, as well as in stainless steels.
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In our Tech Metals Tuesday series, we introduce various metals in video format.
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