Glossary

Tellurium is a metalloid element with the chemical symbol Te and atomic number 52. It shares properties with both metals and nonmetals, sitting alongside selenium and sulfur in the periodic table. Tellurium is silvery-white, brittle, and crystalline, and it has a metallic luster. Though it conducts electricity, it does so poorly at room temperature—its conductivity increases when heated, a hallmark of semiconductors.

In nature, tellurium is extremely rare, ranking among the least abundant elements in Earth’s crust. It is typically found in combination with other metals such as gold, silver, copper, and lead, forming telluride minerals (e.g., calaverite and sylvanite). Because of this, most tellurium is obtained as a byproduct of copper refining, where it is recovered from anode slimes formed during electrolysis.

Chemically, tellurium behaves like selenium and sulfur, forming oxides, halides, and tellurides. It burns in air with a blue flame, producing tellurium dioxide (TeO₂), and it reacts with metals to form compounds used in thermoelectric devices. Tellurium’s most important application is in semiconductor technology, especially in cadmium telluride (CdTe) solar cells, which convert sunlight into electricity efficiently and cost-effectively. It’s also used in thermoelectric materials, where it helps generate power from heat differentials, and in phase-change memory devices used in modern data storage.

In metallurgy, small amounts of tellurium are added to steel, copper, and lead alloys to improve machinability and corrosion resistance. Tellurium enhances the strength, hardness, and durability of these alloys without compromising ductility. It also finds use in rubber vulcanization, glass tinting, and ceramic pigments.

One interesting aspect of tellurium is its distinct garlic-like odor—a characteristic that can persist in the breath or sweat of people exposed to it. While toxic in large doses, trace amounts of tellurium compounds are sometimes used in specialized chemical and industrial applications.