Tellurium is a rare, silvery-white metalloid used primarily in solar panels, thermoelectric devices, data storage discs, and infrared optics. It ranks as the 71st most abundant element in Earth’s crust, roughly on par with platinum and palladium, making it scarce enough that over 90% of the world’s supply comes not from dedicated mining but as a byproduct of copper refining. China produces about 75% of global refined tellurium output, and demand has grown steadily as solar energy and electronics manufacturing have expanded.
Solar Panels
The single largest use of tellurium today is in cadmium telluride (CdTe) thin-film solar cells. These panels are the second most common photovoltaic technology after traditional silicon, accounting for 21% of the U.S. solar market and 4% of the global market as of 2022. Over the past 15 years, CdTe deployment has scaled from megawatts to gigawatts as module efficiency has more than doubled.
CdTe cells earn the “thin-film” label because the material absorbs sunlight more efficiently than silicon, so manufacturers need much thinner layers to capture the same amount of light. That translates to less raw material per panel and lower production costs. The U.S. Department of Energy is currently funding a $20 million consortium, coordinated by the National Renewable Energy Laboratory, with the goal of pushing CdTe cell efficiency to 24% by 2025 and 26% by 2030.
Thermoelectric Cooling and Power Generation
Bismuth telluride has been the go-to material for solid-state heating and cooling for over 60 years. These devices use the Peltier effect: run an electric current through a bismuth telluride thermocouple, and one side gets hot while the other gets cold. You’ll find this technology in portable coolers, temperature-controlled car seats, precision lab instruments, and the cooling systems for laser diodes and computer chips.
The same physics works in reverse. When one side of a bismuth telluride device is exposed to heat and the other to a cooler surface, it generates electricity. This makes it useful for harvesting modest amounts of power from waste heat in industrial settings or remote sensors. Near room temperature, bismuth telluride alloys remain the most efficient thermoelectric material available. Even in systems designed for higher-temperature heat sources, bismuth telluride is used at the cooler end of the device to maximize overall efficiency. Current designs using a heat source around 127°C (400 K) and a water-based heat sink can achieve roughly 2% generation efficiency, enough to power small electronics and sensors in off-grid applications.
Data Storage: Rewritable Discs and Memory Chips
If you’ve ever used a rewritable DVD or Blu-ray disc, tellurium was doing the heavy lifting. The recording layer in these discs is made from a compound of germanium, antimony, and tellurium (known in the industry as GST). This material can switch between a glassy, disordered state and an organized crystalline state in billionths of a second, and each state reflects laser light differently. That’s how the disc stores and erases data.
The same switching principle powers phase-change random access memory (PRAM), a type of non-volatile computer memory. Unlike conventional RAM, PRAM retains data when the power is off, and GST is the most widely used material for it. Researchers continue to study exactly how tellurium atoms move within the material during these rapid phase changes, because understanding that process is key to making faster, more durable memory chips.
Infrared Optics
Tellurium is a core ingredient in chalcogenide glasses, a family of specialty glasses prized for their ability to transmit infrared light far beyond the range of ordinary glass. While sulfur- and selenium-based versions cover the mid-infrared range, tellurium-based glasses push transparency out to 30 micrometers or more. Some experimental compositions incorporating silver iodide have extended that window to 35 micrometers, farther than any other chalcogenide glass family.
This extreme infrared transparency matters for several practical reasons. Many complex molecules, including explosives, have unique infrared “fingerprints” that security scanners can detect. Tellurium-based glass fibers are also being developed for carbon dioxide sensing and for infrared telescopes designed to identify biological molecules on distant planets. These glasses can be shaped into fibers, thin films, and waveguides, making them versatile building blocks for next-generation infrared instruments.
Rubber and Metallurgy
Small amounts of tellurium are added to rubber during vulcanization, the heating process that transforms raw rubber into a durable, elastic material. Tellurium-based additives improve the finished rubber’s resistance to heat and aging, which is why they show up in high-performance hoses, belts, and tire compounds that need to withstand sustained high temperatures.
In metallurgy, trace additions of tellurium improve the machinability of steel and copper alloys. The element makes metal chips break off more cleanly during cutting and drilling, which speeds up manufacturing and extends tool life. Lead-tellurium alloys are used in battery plates and cable sheathing, where the tellurium increases resistance to corrosion and vibration.
Medical Imaging
Tellurium has a niche role in nuclear medicine. The radioactive isotope tellurium-123m has been studied as a component of adrenal-imaging agents, compounds designed to help doctors visualize the adrenal glands during diagnostic scans. These agents concentrate in the adrenal glands after injection, and their radiation doses are comparable to other adrenal-imaging compounds already used clinically. This remains a specialized application, but it illustrates how tellurium’s chemistry allows it to be incorporated into biologically targeted molecules.
Where Tellurium Comes From
Almost all commercial tellurium is extracted from the sludge left behind during electrolytic copper refining. When copper ore is purified using electricity, trace elements like tellurium, selenium, and precious metals settle out as “anode slimes.” Smaller amounts come from lead refinery waste and from the dust and gases released during smelting of bismuth, copper, and lead-zinc ores.
This byproduct status creates an unusual supply dynamic. Tellurium production is tied to copper demand, not tellurium demand. If the solar industry needs more tellurium, producers can’t simply open a tellurium mine. They have to process more copper refinery waste or develop new extraction techniques. That constraint, combined with China’s dominant 75% share of global refined output, has led to tellurium being classified as a critical mineral by several governments concerned about supply chain security for clean energy technologies.
Toxicity
Tellurium is toxic in relatively small amounts, though human exposure is uncommon outside of industrial settings. The most distinctive sign of tellurium poisoning is a persistent garlic-like odor on the breath and skin, caused by the body converting tellurium into dimethyl telluride, a volatile compound it exhales. Animal studies have shown that significant tellurium exposure can damage the protective myelin coating around peripheral nerves, leading to a type of nerve disorder. Workers in copper smelting and electronics manufacturing are the most likely to encounter tellurium dust or fumes, and workplace exposure limits are set very low as a result.