Tellurium (Te52) is a silvery-white brittle element with a metallic luster found in its pure state. This rare element was first discovered in 1782 by Franz Joseph Muller von Reichenstein who was the chief inspector of gold mines in Transylvania at that time. In nature, this element is found fused in telluride ores of gold and silver. There are about 30 isotopes (atoms of the same element with varying number of neutrons) of which 8 are naturally occurring.
The most commonly found isotopes are 128Te and 130Te. Tellurium is a p-type semiconductor with an electrical resistance of 1 ohm at 25ºC. The conductivity increases with exposure to light. Tellurium is one of the metalloids in the periodic table. Metalloids bear properties of both metals and non metals.
Facts about Tellurium
|Number of protons/electrons||52|
|Melting point||449.5 ºC (841.1 ºF)|
|Boiling point||989.8 ºC (1813.64 ºF)|
|Hardness||2 - 2.5|
|Specific gravity||6.1 - 6.3|
Uses of Tellurium
Due to its metalloid properties, it is extensively used in making alloys and semiconductors. Mentioned below are some of the major applications of this element.
One of the prominent uses of tellurium is alloying. An alloy is a mixture of two or more metals fused together in a melting process to enhance properties like ductility and tensile strength. this metalloid is added to metals like lead (Pb) to increase durability and resilience of the metal. Also, tellurium based alloys are not affected by the corrosive action of sulfuric acid (H2SO4). Tellurium is also added to stainless steel and copper (Cu) to increase the ductility in them. Cast iron alloys also contain tellurium which aids in regulation of temperatures.
Tellurium has potential application in making of semiconductors for industrial applications. Tellurium when alloyed with cadmium (Cd) and mercury (Hg) forms a compound mercury cadmium telluride, which serves as an excellent infrared sensitive semiconductor. Organotellurium compounds like dimethyl telluride and diisopropyl telluride are used as precursors for compound semiconductors. Tellurium with bismuth (Bi) finds a potential use in thermoelectric devices. It enhances the effectiveness of the solar cell electric power generation. Hence many solar panels contain cadmium telluride (CdTe) which is a p type semiconductor. When alloyed with zinc, tellurium makes a good gamma ray detector. With mercury, tellurium is used in making versatile infrared detectors.
Tellurium is extensively used in making ceramics, chalcogenide glasses, tinting glasses, blasting caps and initiators that are used in radical polymerization reactions. This is because of the antioxidant activity of the di-tellurides. One of the major uses is in industrial applications like making thermoelectric apparatuses. It is also used in the process of vulcanizing rubber. Tellurium is used as a gasoline additive to reduce engine knocks in automobiles.
Tellurium is cyanogenic by nature and is a radioactive metalloid. Exposure to even 0.01 mg/m2 can result in a "tellurium breath" (garlic odor) followed by dry mouth, headaches, nausea and drowsiness. Inhalation can also cause respiratory tract irritation and eye irritation. Heating tellurium can emit toxic fumes which might create a fire hazard due to its chemical reactions with halogens in the atmosphere. The major producers, today, are Canada, United States, Peru and Japan. A rare metalloid that it is, tellurium with 99.5% purity costs about USD 100/lb. Pertaining to its metalloid characteristics, tellurium is a chemical bonder. The first application of chemical bonding of tellurium was used in making the outer shell of the first atom bomb. Tellurium uses, today definitely find a laudable place in many industrial applications due to the versatile properties of this metalloid.