Impact of the Dopant Species on the Thermomechanical Material Properties of Thermoelectric Mg2Si0.3Sn0.7

Abstract

Thermoelectric generators are an excellent option for waste heat reuse. Materials for such devices have seen their thermoelectric properties improving constantly. The functioning of a generator, however, does not only depend on thermoelectric properties. Thermal and mechanical properties play a decisive role in the feasibility of any thermoelectric generator. To shed light on the properties exhibited by thermoelectric materials, we present the temperature dependent characterization of Young’s modulus and coefficient of thermal expansion for Mg2Si0.3Sn0.7. Comparing undoped to Bi-doped n-type and Li-doped p-type material, we investigated the influence of doping in the relevant temperature regime and found the influences to be minor, proving similar properties for n- and p-type. We found a Young’s modulus of 84 GPa for the p-type and 83 GPa for the n-type, similar to that of the undoped compound with 85 GPa. The thermal expansion coefficients of undoped, as well as n- and p-type were equally similar with values ranging from 16.5 to 17.5 × 10−6 1/K. A phase analysis was performed to further compare the two materials, finding a similar phase distribution and microstructure. Finally, using the gathered data, estimations on the possible thermally induced stresses under a temperature difference are provided to evaluate the relevance of knowing temperature dependent thermal and mechanical properties.

Analyzing the Performance of Thermoelectric Generators with Inhomogeneous Legs: Coupled Material–Device Modelling for Mg2X-Based TEG Prototypes

“…In this study, the solid solution Mg 2 Si 0.3 Sn 0.7 was chosen as the chemical composition for both p-and n-type materials of the TEG. Both materials have similar mechanical properties [48] and have a reported figure of merit among the best in the mid-to high-temperature range. Pictures and dimensions are reported in [29], while a schematic of the prototype is shown in Figure 1.…”

Efficiency Measurement and Modeling of a High‐Performance Mg2(Si,Sn)‐Based Thermoelectric Generator

“…Using chemically similar p‐ and n‐type materials can improve the mechanical stability of the module, even more if the same electrode is used for all legs, as the differential thermal expansion will be similar for all legs. [ 34 ] Some stress due to the remaining coefficient of thermal expansion (CTE) mismatch cannot be avoided; therefore, having the same material combination for all legs can also allow to find means to relieve this stress more easily.…”

Copper Iodide on Spacer Fabrics as Textile Thermoelectric Device for Energy Generation

“…Conventional thermoelectric devices consist of n-and p-type thermoelectric legs. Therefore, materials such as tellurides, as Bi 2 Te 3 or PbTe, half-Heusler compounds, silicides or oxides [25][26][27][28][29] were investigated. However, materials such as carbon nano-tubes (CNT) and poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:pss) are also investigated for stretchable TE devices [30] or on 3D structures [31].…”