Multifunctional GeMnTe 2 Synergistically Optimizes Thermoelectric Properties of SnTe-In 2 Te 3 Alloys.

SnTe-In 2 Te 3 alloys ensure excellent electrical properties in the whole temperature region due to the resonant level. Nevertheless, temperature-sensitive resonance states and single phonon scattering restrict further improvement of thermoelectric performance. Consequently, it is anticipated that additional electrically independent scattering sources should be introduced to impede phonon transport. Here, the SnTe-In 2 Te 3 -GeMnTe 2 alloy is prepared by further solidifying cubic GeMnTe 2 , which demonstrates multiple modulation effects. The highly redissolved Mn 2+ promotes the valence band convergence, enhances the Seebeck coefficient at higher temperature, and balances the possible weakened resonance level effect at higher carrier concentrations, and a high average power factor (1.94 mW m -1 K -2 ) is realized over the entire temperature range. Additionally, compensatory vacancies, substitutions, and Ge/Mn precipitates are easily constructed with GeMnTe 2 alloying, leading to a further reduction in lattice thermal conductivity, which reaches κ l ∼ 0.6 W m -1 K -1 at 850 K. Ultimately, a high peak zT of ∼1.25 (850 K) and a zT ave of 0.72 (300-850 K) are realized in (SnTe) 2.91 (In 2 Te 3 ) 0.03 (Ge 0.5 Mn 0.5 Te) 1.2 , and the maximum thermoelectric conversion efficiency of ∼2.8% (Δ T ∼ 450 K) is achieved. The present results indicate multiple effects of GeMnTe 2 in enhancing the thermoelectric performance of SnTe-In 2 Te 3 alloys.