Thermoelectric Transport in Nanocomposites

Abstract

Thermoelectric materials which can convert energies directly between heat and electricity are used for solid state cooling and power generation. There is a big challenge to improve the efficiency of energy conversion which can be characterized by the figure of merit (ZT). In the past two decades, the introduction of nanostructures into bulk materials was believed to possibly enhance ZT. Nanocomposites is one kind of nanostructured material system which includes nanoconstituents in a matrix material or is a mixture of different nanoconstituents. Recently, nanocomposites have been theoretically proposed and experimentally synthesized to be high efficiency thermoelectric materials by reducing the lattice thermal conductivity due to phonon-interface scattering and enhancing the electronic performance due to manipulation of electron scattering and band structures. In this review, we summarize the latest progress in both theoretical and experimental works in the field of nanocomposite thermoelectric materials. In particular, we present various models of both phonon transport and electron transport in various nanocomposites established in the last few years. The phonon-interface scattering, low-energy electrical carrier filtering effect, and miniband formation, etc., in nanocomposites are discussed.

Thermoelectric properties and low thermal conductivity of nanocomposite ZrTe5 under magnetic field

“…In this case, both electrons and holes contribute to the thermal conductivity, which is coherent with the narrow-bandgap nature of the hand-milled sample. As expected, the ball-milled sample has a much lower thermal conductivity because of the abundant interfaces created by the nanocrystals and defects induced by the Te deficiency that scatters phonons efficiently [34,49]. The thermal conductivity is close to 1 W.m -1 .K -1 throughout the whole temperature range, close to the lower limit value of 0.73 W.m -1 .K -1 estimated theoretically [50].…”

“…The high-energy ball-milling method is well-known to enhance the thermoelectric performance of polycrystalline materials and was successfully applied in different materials such as bismuth telluride and silicon germanium with more than 30% increase in ZT [34,35]. It creates nanocomposites with a microstructure composed of a variety of crystallite sizes ranging from nanometers to micrometers which effectively scatters phonons and achieves a very low thermal conductivity.…”

Doping Effect on Cu2Se Thermoelectric Performance: A Review

“…It will inolve a higher risk of severe pollution to put them into widespread commercial use. Thus, looking for TE materials which are environmentally friendly and have high efficiency becomes a buzz in recent TE materials researches [ 25 , 26 ]. Cu 2 Se is one of the promising materials.…”

Realising the potential of thermoelectric technology: a Roadmap

“…Energy Filtering: 16 The concept is that carriers with a mean energy substantially below the Fermi level are "filtered" by potential barriers and hence do not contribute to transport, enabling a reduction in electrical conductivity and improvement in Seebeck coefficientto be acheived. It was believed to be most effective when the distance between the potential barriers are comparable to the carrier mean free path.…”