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.

Additive manufacturing is a novel and breakthrough technology by which parts can be manufactured for various purposes and services. As in any production process, the desired properties of additively manufactured components, particularly in electron beam melting processes, ultimately depend on the manufacturing process parameters. Process parameters should be designed accordingly to manufacture parts with specific and desired characteristics. This study focuses on examining the effect of process parameters, such as beam current and velocity, focus offset, and line offset, at three different values each, on the properties of Ti-6Al-4V alloy. The study on the effect of the process parameters on the as-built material’s performance was performed using the Taguchi approach using an L₉ (3⁴) orthogonal array. The properties of printed parts (density, surface roughness, elastic moduli, hardness, tensile characteristics, fractography, and microstructure) were tested. A wide range of properties was obtained and analyzed; namely, porosity varied from 8% to almost fully dense materials with density higher than 99.9% and a range of yield and ultimate tensile strength values and brittle samples with less than 1% elongation to ductile samples with an elongation greater than 16%. The overall performance of printed parts was determined based on an evaluation criterion. Several parameter combinations were found and yielded the fabrication of parts with high density and relatively fine microstructure. The comparison of the best parameter combinations determined in this study and the parameters recommended by the machine manufacturer showed that improved results were obtained, and even when using the optimal parameters, they can be improved even more. This result highlights the ability of the proposed DOE method to further develop existing results and even for development of manufacturing parameters for new materials.

Thermoelectric generators (TEGs) are devices capable of transforming heat energy into electricity and vice versa. Although TEGs are known and have been in use for around five decades, they are implemented in only a limited range of applications, mainly extraterrestrial applications. This is due to their low technical readiness level (TRL) for widespread use, which is only at levels of 3–5 approaching laboratory prototypes. One of the most setbacks in reaching higher TRL is the lack of understanding of the mechanical and thermo-mechanical properties of TE materials. Out of ~105,000 entries about TE materials only ~100 entries deal with mechanical properties, while only 3 deal with thermo-mechanical properties. GeTe-based alloys with varying other elements, forming efficient p-type thermoelectric materials in the 200 ÷ 500 °C temperature range, have been intensively researched since the 1960s and have been successfully applied in practical TEGs. Yet, their temperature-dependent mechanical properties were never reported, preventing the fulfillment of their potential in a wide variety of practical applications. The combined effects of temperature and mechanical compression of GeTe were explored in the current research by implementing novel quantitative crystallographic methods to statistically describe dislocation activity and modification of the micro-texture as inflecting by the testing conditions. It is suggested, through utilizing these methods, that the combined effect of compression and temperature leads to the dissolving of twin boundaries, which increases dislocation mobility and results in a brittle-to-ductile transition at ~0.45 of the homologous temperature.