Performance of Thermoelectric Generation Module Using Mg<sub>2</sub>(Si,Sn)-Based Thermoelectric Materials

Mg2(Si,Sn) solid-solution thermoelectric materials were synthesized by Spark Plasma Sintering to investigate their temperature-dependent transport properties. Both n-type and p-type samples exhibit behavior characteristic of heavily doped semiconductors, with increased power factor and reduced lattice thermal conductivity up to the intermediate-temperature range. As a result, zT peaks at around 623–673 K, reaching ≈1.2 for n-type and ≈0.5 for p-type. At higher temperatures, intrinsic excitation induces minority carriers and bipolar thermal conduction, leading to reduced Seebeck coefficient and increased thermal conductivity, thus lowering zT. A prototype thermoelectric module consisting of 32 p–n couples was fabricated using the developed materials. The module exhibits a nearly linear increase in output voltage with ΔT and maintains stable internal resistance, although assembly-related losses increased the total resistance. The module provided 7.8 W of output power and an efficiency of ∼7.5% at ΔT = 470 K. These results confirm the suitability of Mg2(Si,Sn) for medium-temperature power generation and highlight pathways for further optimization.