MATERIALS PHYSICS

A Route to Cooler Thermoelectrics

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Science  24 Nov 2000:
Vol. 290, Issue 5496, pp. 1465
DOI: 10.1126/science.290.5496.1465a

Thermoelectric devices generally consist of a junction of two materials possessing different electrical and thermal conductivity properties. When exposed to a thermal gradient, an electrical current flows from one material to the other. Conversely, passing a current through the junction can result in cooling. Such devices are attractive as refrigerators or possibly as power generators to scavenge waste heat.

Thermoelectrics should have low thermal conductivity, high electrical conductivity, and high thermopower, properties that can be difficult to optimize simultaneously in a specific material. They are rated by a figure-of-merit, ZT (where T is temperature). Most good thermoelectrics have ZTs around unity, which is about the break-even point for practical applications. Rontani and Sham propose a method for increasing ZT to 3 or 4. Their calculations show that by introducing a layer of rare-earth atoms at the interface of a metal-ferroelectric junction, the electronic interactions should give rise to a sharp variation in the carrier transmission across the junction and a high thermopower. The large thermal impedance mismatch between the two materials should also decrease the thermal conductivity while maintaining good electrical conductivity and lead to a significant increase in ZT for low-temperature operations. — ISO

Appl. Phys. Lett. 77, 3033 (2000).

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