Nanocomposites with High Thermoelectric Figures of Merits

Applications

Nanocomposites made of semiconductor nanoparticles impregnated in a semiconductor host material have a high thermoelectric figure-of-merit and can be used to make solid-state refrigerators and solid-state power generators. These refrigerators can be used for thermal management of microdevices or in large scale applications. Generators can convert heat (from any heat source) into electricity for automobiles, distributed power sources, battery chargers, or portable power sources.

Problem Addressed

Thermoelectric refrigerators are environmentally benign, quiet, and scalable; however their efficiency is limited by the material figure-of-merit – the thermoelectric figure-of-merit (Z) times the absolute temperature ZT. Nanostructured materials have led to significant enhancement in ZT. This technology uses nanocomposites synthesized from wet-chemistry and physical vapor condensation to create a scalable and economical thermoelectric refrigerators or generators.

Technology

The nanocomposites can either be nanoparticles or nanowires in the range of 2-80nm in diameter. The thermoelectric figure-of-merit (Z) is proportional to the Seebeck coefficient and the electrical conductivity, but inversely proportional to the thermal conductivity. Therefore, to maximize the Z the material should minimize electron scattering (maximize electrical conductivity) and maximize phonon scattering (minimize thermal conductivity). There are two ways to achieve this, one is that the nanoparticles and the host medium have similar bandgaps and the other is that the nanoparticle has a lower potential minimum than that of the host media. The nanocomposites are fabricated using existing nanoparticle techniques (ball-milling, vapor-liquid-solid condensation, etc.) and then the nanoparticles can be embedded by placing them in a liquid host and then cooling the composite.

Advantages

  • Improves scalability of nanocomposites
  • Cheaper than previous fabrication techniques