by U.S. Geological Survey Wednesday, June 13, 2018
U.S. Geological Survey tellurium commodity specialist Micheal W. George has compiled the following information on tellurium, a rare and expensive metal.
A relatively rare element, tellurium is tied with platinum and palladium as the 71st most abundant element in Earth’s crust. Tellurium belongs to the chalcogen chemical family, along with oxygen, sulfur, selenium and polonium. Oxygen and sulfur are nonmetals, polonium is a metal, and selenium and tellurium are metalloids. However, selenium and tellurium are often referred to as metals when in elemental form, and have semiconducting electrical properties that make them suitable in electronic applications.
Tellurium is currently recovered as a byproduct of nonferrous metal mining, principally from the anode slimes associated with electrolytic refining of copper. In copper ores, tellurium forms stable crystalline compounds (called tellurides) of gold, silver, bismuth, mercury, platinum and palladium that tend to accumulate in residual ore fluids.
The element was first identified in 1782 in Transylvanian gold ore. For more than a century, tellurium was considered an experimental material having little commercial value. It eventually became useful as an alloying additive used in steel and nonferrous alloys to improve machining characteristics and to stabilize cast iron.
Today, tellurium is used in cadmium telluride thin-film solar cells, which are becoming increasingly efficient and cost competitive. In addition to solar cells, tellurium in the form of semiconducting bismuth telluride is used in thermoelectric cooling devices for military and electronics applications, such as the cooling of infrared detectors, integrated circuits, laser diodes and medical instruments.
As of 2010, the estimated use of tellurium was 40 percent in solar photovoltaics, 30 percent in thermoelectric devices, 15 percent in metallurgy, 5 percent in rubber applications and 10 percent in other applications.
Owing to increases in solar cell production in the United States and Europe and thermoelectronics in China, the global demand for tellurium in recent years has increased significantly. Despite increasing demand, estimated global production has remained relatively unchanged while surplus inventories have been exhausted. Consequently, the annual average price of tellurium jumped to $349 per kilogram in 2011, up from $82 per kilogram in 2007.
Due to the rapid increase in price, metallurgical demand for tellurium dropped; meanwhile demand for high-purity tellurium, used in electronics applications such as solar photovoltaics and thermoelectric devices, increased.
In 2012, the solar cell market became oversupplied, several solar manufacturers filed for bankruptcy or curtailed some of their production, and the price of tellurium dropped dramatically.
In anticipation of renewed demand in the future, production from sources other than copper anode slimes is expected to increase. In China, a primary tellurium mine is operating, and companies are exploring for, and developing, deposits of gold telluride around the world.
For more information on tellurium and other mineral resources, visit minerals.usgs.gov/minerals.
TELLURIUM PRODUCTION AND CONSUMPTION
In 2011, estimated world production was 500 to 550 metric tons.
About 90 percent of global tellurium production comes from anode slimes generated from electrolytic copper refining.
Canada, China, Japan, Peru, Russia and the United States are the leading producers of tellurium.
In the United States, only one company produces commercial-grade tellurium at a refinery in Texas.
The name “tellurium” is from the Latin “tellus,” which means earth.
Tellurium is used in new phase-change memory chips.
Sensitivity to light changes the electrical properties of tellurium compounds, which are a component of special glass used in infrared guided missiles.
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