Seebeck effect
Definition and meaning of Seebeck effect in chemistry.
The Seebeck effect is the generation of an electrical voltage when two different electrical conductors or semiconductors are joined together and exposed to a temperature difference. The voltage produced, called the thermoelectric EMF, is proportional to the temperature difference and the Seebeck coefficient of the materials.
In more detail
When a temperature gradient is applied across a junction of two dissimilar materials, the charge carriers (electrons or holes) diffuse from the hot end toward the cold end, driven by the temperature gradient and their interaction with the material's atomic lattice. This creates a charge imbalance between the two ends, with the direction depending on the dominant charge carrier: materials with a negative Seebeck coefficient (electron-dominated conduction) develop one polarity, while materials with a positive Seebeck coefficient (hole-dominated conduction) develop the opposite polarity. The resulting charge separation produces a measurable voltage. The Seebeck effect is the foundation of thermoelectric devices and is most famously used in thermocouples for precise temperature measurement. The effect is named after Thomas Johann Seebeck, who discovered it in 1821, and it is thermodynamically related to the Peltier effect, which produces cooling or heating when an electrical current is applied.
Key facts
| Field | Physical Chemistry |
|---|---|
| Seebeck Coefficient | Typically -200 to +200 microvolts per Kelvin, depending on material |
| Discovered | 1821 by Thomas Johann Seebeck |
| Primary Application | Temperature measurement with thermocouples and thermoelectric generators |
A copper-constantan (copper-nickel alloy) thermocouple generates approximately 40 microvolts per Kelvin of temperature difference, making it a practical tool for measuring temperature across a range from negative 200 degrees Celsius to 350 degrees Celsius.
Frequently asked questions
What is a Seebeck coefficient?
The Seebeck coefficient is a material property (expressed in microvolts per Kelvin) that quantifies how much thermoelectric voltage a material generates per unit temperature difference. It is temperature-dependent and varies significantly between different metals, semiconductors, and alloys.
How does the Seebeck effect relate to the Peltier effect?
The Seebeck and Peltier effects are reciprocal thermoelectric phenomena. The Seebeck effect converts a temperature difference into an electrical voltage, while the Peltier effect converts an electrical current into a temperature difference (heating or cooling at a junction).