Enhanced Thermoelectric ZT in the Tails of the Fermi Distribution via Electron Filtering by Nanoinclusions -- Model Electron Transport in Nanocomposites

TL;DR

This paper demonstrates that nanoinclusions in silicon carbide/silicon composites enhance thermoelectric performance by energy-selective electron filtering, confirmed through modeling and experiments, leading to higher ZT values.

Contribution

It introduces a model showing how nanoinclusions induce energy filtering of electrons, significantly improving thermoelectric efficiency in nanocomposites.

Findings

Silicon carbide nanoinclusions increase ZT by enhancing the Seebeck coefficient.

Energy-dependent electron scattering explains the thermoelectric improvements.

Theoretical modeling aligns with experimental results.

Abstract

Silicon carbide nanoparticles with diameters around 8 nm and with narrow size distribution have been finely mixed with doped silicon nanopowders and sintered into bulk samples to investigate the influence of nanoinclusions on electrical and thermal transport properties. We have compared the thermoelectric properties of samples ranging from 0-5% volume fraction of silicon carbide. The silicon carbide nanoinclusions lead to a significant improvement in the thermoelectric figure of merit, ZT, largely due to an enhancement of the Seebeck coefficient. A semiclassical Boltzmann transport equation is used to model the electrical transport properties of the Seebeck coefficient and electrical conductivity. The theoretical analysis confirms that the enhancements in the thermoelectric properties are consistent with the energy selective scattering of electrons induced by the offset between the silicon Fermi level and the carbide conduction band edge. This study proves that careful engineering of the energy-dependent electron scattering rate can provide a route towards relaxing long-standing constraints in the design of thermoelectric materials.