Effect of In and Cd co-doping on the thermoelectric properties of Sn1−xPbxTe

Pristine tin telluride (SnTe) with a similar electronic structure to PbTe shows inferior thermoelectric performance owing to high p -type hole concentration (10 21 cm −3 ), high lattice thermal conductivity, κ latt (∼2.8 W mK −1 at room temperature) and large energy gap between light and heavy hole valence bands. Interestingly, 30 mol% substitution of lead in SnTe decreases the excess hole carrier concentration and lattice thermal conductivity (∼0.67 W m −1 K −1 at 300 K) significantly. Here, we report the promising thermoelectric performance in Sn 0.70 Pb 0.30 Te by enhancing the Seebeck coefficient via the co-adjuvant effect of resonant level formation and valence band convergence. We obtain a Seebeck coefficient value of ∼141 μ V K −1 at 300 K, which further increases to ∼260 μ V K −1 at 708 K for Sn 0.70 Pb 0.30 Te—3% Cd and 0.50% In sample. This is one of the highest S values for SnTe based system, to the best of our knowledge. In and Cd have discrete but complementary roles to augment the Seebeck coefficient value of Sn 0.70 Pb 0.30 Te where In acts as a resonant dopant and Cd serves as valence band convergent, respectively, as demonstrated by the well-known Pisarenko plot of SnTe. Finally, we have achieved a maximum thermoelectric figure of merit, zT, of ∼0.82 at 654 K for Sn 0.70 Pb 0.30 Te—3% Cd and 0.25% In sample.