Achieving Enhanced Thermoelectric Performance in (SnTe)_1-<i>x</i>(Sb₂Te₃)<i>_x</i> and (SnTe)_1-<i>y</i>(Sb₂Se₃)<i>_y</i> Synthesized via Solvothermal Reaction and Sintering

Abstract

SnTe is proposed to be an intriguing low-toxicity alternative to PbTe. Herein, we report the diminished lattice thermal conductivity (κ_L) and enhanced <i>zT</i> of SnTe by way of vacancy engineering. (SnTe)_1-<i>x</i>(Sb₂Te₃)<i>_x</i> (<i>x</i> = 0.03, 0.06, and 0.10) and (SnTe)_1-<i>y</i>(Sb₂Se₃)<i>_y</i> (<i>y</i> = 0.03 and 0.06) were synthesized by blending and sintering their solution-synthesized nano/microstructures (i.e., SnTe octahedral particles, Sb₂Te₃ nanoplates, and Sb₂Se₃ nanorods). Benefiting from the chemical reactions during sintering, single-phase SnTe-based solid solutions were formed when <i>x</i> or <i>y</i> is not higher than 0.06, into which tunable concentrations of Sn vacancies were introduced. Such vacancies significantly enhance phonon scattering, leading to the sharply reduced room temperature κ_L of 1.40 and 1.26 W m^-1 K^-1 for <i>x</i> = 0.06 and <i>y</i> = 0.06 samples, respectively, as compared to 3.73 W m^-1 K^-1 for pristine SnTe. Enabled by point defects with the highest concentration and SnSb₂Te₄ secondary phase, (SnTe)_0.90(Sb₂Te₃)_0.10 sample obtains the lowest κ_L of 0.70 W m^-1 K^-1 at 813 K. Ultimately, maximum <i>zT</i> values of 0.6 and 0.7 at 813 K are achieved in (SnTe)_0.90(Sb₂Te₃)_0.10 and (SnTe)_0.94(Sb₂Se₃)_0.06, respectively. This study demonstrates the effectiveness of vacancy engineering in improving <i>zT</i> of SnTe-based materials.