Simulation of Morphological Effects on Thermoelectric Power, Thermal and Electrical Conductivity in Multi‐Phase Thermoelectric Materials

Abstract

Multi-phase thermoelectric materials are mainly investigated these days due to their potential of lattice thermal conductivity reduction by scattering of phonons at interfaces of the involved phases, leading to the enhancement of expected thermoelectric efficiency. On the other hand, electronic effects of the involved phases on thermoelectric performance are not always being considered, while developing new multi-phase thermoelectric materials. In this chapter, electronic effects resulting from controlling the phase distribution and morphology alignment in multi-phase composite materials is carefully described using the general effective media (GEM) method and analytic approaches. It is shown that taking into account the specific thermoelectric properties of the involved phases might be utilized for estimating expected effective thermoelectric properties of such composite materials for any distribution and relative amount of the phases. An implementation of GEM method for the IV-VI (including SnTe and GeTe), bismuth telluride (Bi 2 Te 3 ), higher manganese silicides (HMS) and half-Heusler classes of thermoelectric materials is described in details.

Bismuth Telluride Solubility Limit and Dopant Effects on the Electronic Properties of Lead Telluride

“…In order to further investigate the electronic contribution of the secondary phase due to the geometrical morphology and amount, the general effective media (GEM) approach was applied [6]. The effective thermoelectric transport properties, for composite materials consisting of two separate phases, were calculated based on the effective thermal conductivity, κ eff , and effective electrical resistivity, ρ eff , calculated using Eq.…”

“…Moreover, to the best of our knowledge, most of the previous researches did not investigated the individual electronic contributions of the involved secondary phases embedded in the matrix on the effective thermoelectric transport properties. The general effective media (GEM) approach [6] enables to estimate the transport properties based on experimentally measured properties of each of the involved phases. Since the approach is taking into consideration geometrical aspects, it can be utilized for maximizing the thermoelectric figure of merit of composite materials by artificial alignment of the embedded secondary phase in the composite.…”

Physical Metallurgy Inspired Nano‐Features for Enhancement of Thermoelectric Conversion Efficiency

“…In turn, the TE properties of the matrix phase are optimized in terms of dopant selection; the former may, of course, vary upon heat treatments. In case of significant amount of the second‐phase volume fraction, treatment in the framework of the general effective medium (GEM) approach is required . Other side effects may also be considered, such as electron energy filtering …”