What is tellurium?
Tellurium (symbol Te) is element 52 on the periodic table, a metalloid in period 5, group 16. Rare on Earth, common in the universe, and the element that makes rewritable optical discs work. At room temperature it is a solid.
The story
What tellurium is, and how we found it
Rare on Earth, common in the universe, and the element that makes rewritable optical discs work.
The discovery of tellurium
The Accidental Discovery in Gold Country
Transylvania, 1782
Franz-Joseph Müller von Reichenstein, chief inspector of mines in Transylvania (now Romania), encountered a peculiar metallic ore in the Zlatna gold mines. Local miners called it "aurum paradoxum" (paradoxical gold) because it resembled gold but behaved strangely when processed.
The Chemical Detective Work
Müller spent three years investigating this mysterious substance:
- 1782: Initial chemical tests showed it wasn't antimony, bismuth, or any known metal
- 1783: Proved it contained a new metallic element combined with gold
- 1784: Isolated the element but couldn't determine its exact nature
Berlin Confirmation
Martin Heinrich Klaproth (1798), the renowned German chemist who discovered uranium and zirconium, confirmed Müller's work. Klaproth independently isolated tellurium from the same Transylvanian ore, verified its elemental nature and named it tellurium (Latin tellus, earth); Müller had called it metallum problematicum.
Early Misunderstandings
For decades, tellurium was confused with selenium due to similar properties:
- Color Changes: Both elements formed colored compounds
- Metalloid Behavior: Similar semiconductor properties
- Chemical Similarity: Both belonged to the same chemical group
- Rarity: Both were extremely rare in pure form
The Gold Connection Revealed
1860s Discovery: Geologists realized that tellurium-rich gold ores in places like Cripple Creek, Colorado, and Kalgoorlie, Australia, contained some of the world's richest gold deposits. Tellurides became synonymous with bonanza gold strikes.
Industrial Applications Emerge
- 1900s: Tellurium used in cast iron and steel alloys for improved machinability
- 1920s: Discovery of thermoelectric properties in bismuth telluride
- 1940s: Military applications in infrared detection systems
- 1960s: Semiconductor research revealed unique electronic properties
Solar Cells
1970s Breakthrough: Scientists at the University of Delaware developed the first efficient cadmium telluride solar cells, launching tellurium's most important modern application. This discovery transformed an obscure metalloid into a critical material for renewable energy.
Digital Age Applications
1990s-2000s: Phase-change memory research revealed tellurium's unique ability to rapidly switch between crystalline and amorphous states, enabling:
- Rewritable optical media (CDs, DVDs, Blu-ray)
- Next-generation computer memory
- High-speed data storage systems