Realization of Large Thermopower Using Semimetals and Narrow-Gap Semiconductors in a Magnetic Field
Thermoelectric materials are vital for the development of thermoelectric generators and coolers used in manufacturing processes. These materials can save energy and money with heating processes.
Researchers
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apparatus, systems, and methods for generating thermopower
United States of America | Granted | 10,439,123
Figures
A thermoelectric device 100 for generating heat flows under a magnetic field. The device contains a thermoelectrode 110 made of a small band gap material. It also includes a magnetic field source 120, operably coupled to the thermoelectrode to apply a magnetic field 125 on the thermoelectrode. There is also a voltage source 130 operably coupled to the thermoelectrode applying an electric field along a perpendicular direction to generate a heat fl
A thermocouple 300 using thermoelectrodes. The In operation, a voltage source can be employed to apply an electric field on the two thermoelectrodes 310 a and 310 b so as to heat or cool objects attached to the thermocouple 300 (e.g., attached to the electrode 320). In another example, the electrode 320 can be coupled to a heat source (e.g., waste heat from vehicle engines) so as to generate electricity in the circuit including the resistor 340.
Technology
The limitations of metals and insulators can be overcome through the use of doped nodal semimetals in a strong magnetic field. The magnetic field ensures that the transverse drift of both electrons and holes contribute additively to the thermopower. Within a sufficiently high magnetic field, a large enhancement of the electronic density of states and a reduction in the Fermi energy occurs. Since the thermoelectrode materials have small band gaps and electron-hole symmetry in their band structure, concentrations of thermally excited electrons and holes both grow - even while their difference remains fixed. These magnetic field effects allow the thermopower to grow without saturation.
Problem Addressed
Thermoelectric materials are a useful tool in generating power from waste heat or transforming electric current into cooling power. Finding materials with large thermopower is vital for the development of thermoelectric generators and thermoelectric coolers. The effectiveness of a thermoelectric material for power applications is quantified by its thermoelectric figure of merit, ZT. In an insulator, thermopower is large, but since conductivity is low, ZT is characteristically low. Metals have robust conductivity yet lack strong thermopower so they yield relatively low ZT.
Advantages
- Substantial thermopower generated from device is amplified by magnetic field allowing ZT to grow without saturation
- Generates an electric field/cooling effect along two directions
Publications
"Large, Nonsaturating Thermopower in a Quantizing Magnetic Field." Science Advances, May 25, 2019. doi: EAAT2621.
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