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.

The recent energy demands affected by the dilution of conventional energy resources and the growing awareness of environmental considerations had motivated many researchers to seek for novel renewable energy conversion methods. Thermoelectric direct conversion of thermal into electrical energies is such a method, in which common compositions include IV-VI semiconducting compounds (e.g., PbTe and SnTe) and their alloys. For approaching practical thermoelectric devices, the current research is focused on electronic optimization of off-stoichiometric p-type PbxSn1−xTe alloys by tuning of Bi2Te3 doping and/or SnTe alloying levels, while avoiding the less mechanically favorable Na dopant. It was shown that upon such doping/alloying, higher ZTs, compared to those of previously reported undoped Pb0.5Sn0.5Te alloy, were obtained at temperatures lower than 210–340 °C, depending of the exact doping/alloying level. It was demonstrated that upon optimal grading of the carrier concentration, a maximal thermoelectric efficiency enhancement of ∼38%, compared to that of an undoped material, is expected.

Abstract

No abstract

No abstract