Properties

General data

Name, symbol, atomic number 

Tellurium, Te, 52

Element category

Metalloid

Melting point 

722.7 K (449.5 °C)

Boiling point 

1261 K (988 °C) 

Crystal structure 

Trigonal

Density

6.232 g/cm³ (at 20 °C)

Mohs hardness

2,25

Specific electrical resistance

approx. 0.01–0.24 Ω·cm (at 20 °C), depending on the material's condition and crystal structure

Physical properties

Unique Crystal Structure Affects Electrical and Thermal Conductivity

Tellurium is a silvery-white, metallic-looking semimetal that is soft and brittle. It can be easily ground into a powder. At room temperature, tellurium is a solid and has a higher density than germanium, for example. 

Tellurium is a semiconductor. Its electrical conductivity increases as the temperature rises or when exposed to light. A distinctive feature of tellurium is that it conducts electricity and heat differently depending on the direction within the crystal. This is due to its crystal structure: the tellurium atoms are arranged in spiral chains. 

These properties make tellurium particularly attractive for electronic and energy-related applications. Compounds with other elements are especially important in this context. Bismuth telluride, for example, is used in thermoelectric components, while cadmium telluride serves as a semiconductor material for thin-film solar cells. 

Characteristic properties

Tellurium behaves unusually when heated

When heated, tellurium does not expand equally in all directions. Along one axis of its crystal structure, it actually contracts, while it expands in other directions. This is due to the unique arrangement of its atoms within the crystal. 

Meaning and applications

Energy Transition: Tellurium Is Gaining Importance

Discovered in 1782 by the mineralogist Franz Joseph Müller von Reichenstein, this semimetal plays an important role today in industrial and technological applications. For a long time, tellurium was used primarily in alloys and thermoelectric components. 

Today, photovoltaics is by far the most important application. When combined with cadmium, it forms cadmium telluride (CdTe), a semiconductor material used in thin-film solar cells. This sector now accounts for about 70 percent of global tellurium consumption. 

As solar energy expands, tellurium is becoming increasingly important. At the same time, its supply is limited, since this semimetal is primarily obtained as a byproduct of copper refining. Other applications include thermoelectrics, metallurgy, and electronics.