Part of the book: Sintering Techniques of Materials
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 (Bi2Te3), higher manganese silicides (HMS) and half‐Heusler classes of thermoelectric materials is described in details.
Part of the book: Thermoelectrics for Power Generation
Thermoelectric (TE) direct conversion of thermal energy into electricity is a novel renewable energy conversion method currently at a technological readiness level of 3–5 approaching laboratory prototypes. While approaching practical thermoelectric devices, an increase in the thermoelectric element’s efficiency is needed at the entire service temperature range. Yet, the main focus of research was concentrated on the electronic properties of the materials, while research on the mechanical properties was left behind. As it is shown in this chapter, knowing and controlling the mechanical properties of TE materials are paramount necessities for approaching practical TEGs. The material’s elastic constants, strength and fracture toughness are the most crucial parameters for designing of practical devices. The elastic constants provide understanding about the material’s stiffness, while strength provides the loading conditions in which the material will keep its original shape. Knowing the fracture toughness provides the stress envelope in which the material could operate and its susceptibility to inherent fabrication faults. The characterization methods of these properties are varied and may be physical or pure mechanical in nature. It is the authors opinion to prefer the mechanical methods, so the results obtained will describe more accurately the material’s response to mechanical loading.
Part of the book: Bringing Thermoelectricity into Reality
The demand for energy efficiency has motivated many researchers to seek for novel methods capable of enhancing the conversion of heat to electricity. Most of the recently published methods for thermoelectric (TE) efficiency enhancement discuss on the reduction of the lattice thermal conductivity, with a minor focus on improved electronic optimization. This is attributed mainly to the fact that the electronic properties are correlated and opposing each other upon increasing the carrier concentration. It has been reported that the system of PbTe-BiTe has potentially high TE performance; this chapter is focused on a detailed investigation of the co-effect of bismuth as an effective electronic dopant and at the same time, as a second phase promoter in the PbTe matrix. (PbTe)x(BiTe)1−x alloys were thermoelectrically examined and the values were analyzed analytically by the general effective media (GEM) approach.
Part of the book: Advanced Thermoelectric Materials for Energy Harvesting Applications