Where Found (Encyclopedia of Global Resources)
Tellurium is uncommon but widely distributed in the Earth’s crust. It has been found in small amounts as an uncombined element but is most often found in various compounds. These compounds occur in sulfide deposits or in ores of gold, copper, and lead.
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Primary Uses (Encyclopedia of Global Resources)
Technical Definition (Encyclopedia of Global Resources)
Tellurium (abbreviated Te), atomic number 52, belongs to Group VIA of the periodic table of the elements and resembles selenium in its chemical and physical properties. It has eight stable isotopes and an average atomic weight of 127.6. Pure tellurium exists as brittle, silver-white crystals or as a dark gray or brown powder. Its density is 6.24 grams per cubic centimeter; it has a melting point of 449.8° Celsius and a boiling point of 989.9° Celsius.
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Description, Distribution, and Forms (Encyclopedia of Global Resources)
Tellurium is a widely distributed element resembling selenium. It usually occurs in compounds with copper, lead, silver, gold, iron, or bismuth. The most important sources of tellurium are ores mined for copper, lead, and gold. The most important producers of tellurium are Canada, the western United States, and Peru. Tellurium is nonrenewable, and investigations into the recovery of tellurium from gold and lead-zinc ores is ongoing.
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History (Encyclopedia of Global Resources)
Tellurium was discovered in 1782 by the Austrian mining inspector Franz Joseph Müller von Reichenstein. It was not isolated as a free element until 1798 and not used for practical purposes until the middle of the twentieth century.
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Obtaining Tellurium (Encyclopedia of Global Resources)
Tellurium is usually obtained as a by-product of copper production. After copper is removed from processed ore by electrolysis, the remaining material contains tellurium as well as silver, gold, and selenium. The tellurium is separated out by treating the material with a base, then neutralizing it. This produces impure tellurium dioxide. This compound can be purified by repeatedly dissolving it and recrystallizing it. Free tellurium metal may be obtained by electrolysis.
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Uses of Tellurium (Encyclopedia of Global Resources)
Tellurium is added to steel to improve its machinability and added to copper to create an alloy with good machinability and high electrical and thermal conductivity. It also increases the ductility of aluminum alloys, the hardness and strength of tin alloys, and the resistance to corrosion of lead alloys. Rubber may be treated with tellurium to improve its aging and mechanical properties. Tellurium has also been used alone or with platinum as a catalyst for chemical reactions.
Tellurium compounds are used in thermoelectric devices. Lead telluride is used to make devices that produce electricity when heated. Bismuth telluride is used to manufacture devices that transfer heat when electricity passes through them.
Tellurium is most important as a steel additive and secondarily as an alloy in copper (to improve its machinability while maintaining conductivity), lead (to dampen vibration and lessen metal fatigue), and cast iron (to reduce depth of chill). It is also used in photoreceptors, in blasting caps, in thermal cooling devices, and as a catalyst in the production of synthetic fibers. Tellurium has been added to glass and ceramics to alter the pigments of these products. An increasingly important application is in the manufacture of solar cells, accounting for an increased demand for high-grade tellurium.
Although tellurium is a toxic substance, serious poisonings are rare. Symptoms caused by tellurium...
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Further Reading (Encyclopedia of Global Resources)
Natural Resources Canada. Canadian Minerals Yearbook, 2005: Selenium and Tellurium. http://www.nrcan.gc.ca/smm-mms/busi-indu/cmy-amc/content/2005/50.pdf
U.S. Geological Survey. Mineral Information: Selenium and Tellurium Statistics and Information. http://minerals.usgs.gov/minerals/pubs/commodity/selenium/
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Tellurium (Chemical Elements)
The elements that make up Group 16 (VIA) of the periodic table are sometimes called the chalcogens. This name comes from the Greek word for "bronze ore," chalkos. The first two elements in the family, oxygen and sulfur, are often found in such ores. Tellurium is the next to last member of that family. The periodic table is a chart that shows how chemical elements are related to one another.
The chalcogens are one of the most interesting families in the periodic table. The first member, oxygen, is a gas with very unmetal-Like properties. The next two members of the family, sulfur and selenium, are solids, with increasingly metallic properties. Tellurium, near the bottom of the family, looks and behaves very much like most metals. The slow change of properties, from less metal-like to more metal-like, occurs in all families in the periodic table. But the change is seldom as dramatic as it is in the chalcogens.
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