Seebeck Effect

The Seebeck effect is the phenomenon in which an electrical potential difference arises in a closed circuit formed by joining two different conductive or semiconductive materials when a temperature difference is created between their junctions. It was discovered in 1821 by the German physicist Thomas Johann Seebeck. Seebeck observed that when he heated one junction of a circuit made from two dissimilar metal wires the compass needle deflected and initially believed the effect to be magnetic. However it was later determined that the phenomenon resulted from an electric current generated by the temperature difference.

Seebeck effect (generated by artificial intelligence)

Physical Mechanism

Under a temperature gradient charge carriers electrons or holes within the material migrate from the hot end to the cold end. This carrier migration creates an imbalance in charge distribution leading to the formation of an electric field along the material. Thus the temperature difference is converted into an electrical potential. The resulting potential difference voltage is proportional to the product of the material’s Seebeck coefficient and the temperature difference.

Mathematical Expression

The Seebeck effect is described by the following equation:

Generated by artificial intelligence

Where:

• ΔV: the generated thermoelectric voltage in volts,
• ΔT: the temperature difference in kelvins,
• α: the Seebeck coefficient in volts per kelvin.

The Seebeck coefficient α is a property of the material and the magnitude of the overall effect is determined by the difference between the Seebeck coefficients of the two materials used.

Seebeck Coefficient and Material Properties

The Seebeck coefficient is a fundamental parameter that determines how much thermoelectric voltage a material can generate. It can be positive or negative depending on the type of dominant charge carrier electrons or holes in the material. For example:

• Iron: +19 μV/K at 0 °C,
• Constantan: –35 μV/K at 0 °C.

Materials with high Seebeck coefficients are preferred for producing more efficient thermoelectric converters.

Applications

1. Thermocouples

Thermocouples are widely used devices for temperature measurement. They consist of two dissimilar metals joined at their ends and generate a voltage via the Seebeck effect which correlates to temperature.

2. Thermoelectric Generators (TEG)

These are systems that directly convert thermal energy into electrical energy. Examples include radioisotope thermoelectric generators in spacecraft industrial waste heat recovery systems and energy harvesting systems in rural areas.

3. Embedded Sensor Systems

They are used particularly to power sensors on road surfaces by harvesting energy from asphalt. This eliminates the need for wiring.

Advantages and Limitations

Advantages

• No moving parts and requires no maintenance.
• Quiet and long-lived.
• Suitable for microscale systems.

Limitations

• Low energy conversion efficiency 5–10%.
• Requires high temperature gradients and specialized materials for high performance.

Related Effects

• Peltier Effect: Heat is exchanged at the junctions when an electric current is applied. It is the reverse of the Seebeck effect.
• Thomson Effect: Observed when both a temperature gradient and an electric current exist along the same material.

Current Research and Developments

Current research focuses on enhancing the performance of thermoelectric materials through nanostructuring high-mobility semiconductors and novel physical phenomena based on spin such as the spin Seebeck effect. These efforts aim to develop more efficient thermoelectric devices.