Thermoelectric Generator Performance Evaluation of Mg₃Sb_0.6Bi_1.4 for Low-Grade Heat Recovery

Bismuth-rich compositions of Mg3Sb2–xBix can be potential low-cost replacements for Bi2Te3-based materials for near-room-temperature thermoelectric applications. The x = 1.4 composition, i.e., Mg3Sb0.6Bi1.4, has been reported to have the best performance, and its thermoelectric generator (TEG) performance has been studied in this work. A single-leg TEG device has been fabricated using iron as the contact material. Interface studies indicate a well-bonded, crack-free joint with a low contact resistance value of 15 μΩ cm2. TEG measurements have been performed with a maximum temperature gradient (ΔT) of 246 K, and a peak efficiency value of 6.5% and a power output of 64 mW have been obtained. Validation of the experimental data has been carried out using theoretical calculations based on a mixed averaging technique and indicates an acceptable match between experiment and theory. The obtained conversion efficiencies of Mg3Sb0.6Bi1.4 are comparable to commercial Bi2Te3 modules in the ΔT range of 50–250 K, indicating their suitability for low-grade heat recovery.