High Thermoelectric Performance of p-Type SnTe via a Synergistic Band Engineering and Nanostructuring Approach

Abstract

SnTe is a potentially attractive thermoelectric because it is the lead-free rock-salt analogue of PbTe. However, SnTe is a poor thermoelectric material because of its high hole concentration arising from inherent Sn vacancies in the lattice and its very high electrical and thermal conductivity. In this study, we demonstrate that SnTe-based materials can be controlled to become excellent thermoelectrics for power generation via the successful application of several key concepts that obviate the well-known disadvantages of SnTe. First, we show that Sn self-compensation can effectively reduce the Sn vacancies and decrease the hole carrier density. For example, a 3 mol % self-compensation of Sn results in a 50% improvement in the figure of merit ZT. In addition, we reveal that Cd, nominally isoelectronic with Sn, favorably impacts the electronic band structure by (a) diminishing the energy separation between the light-hole and heavy-hole valence bands in the material, leading to an enhanced Seebeck coefficient, and (b) enlarging the energy band gap. Thus, alloying with Cd atoms enables a form of valence band engineering that improves the high-temperature thermoelectric performance, where p-type samples of SnCd(0.03)Te exhibit ZT values of ~0.96 at 823 K, a 60% improvement over the Cd-free sample. Finally, we introduce endotaxial CdS or ZnS nanoscale precipitates that reduce the lattice thermal conductivity of SnCd(0.03)Te with no effect on the power factor. We report that SnCd(0.03)Te that are endotaxially nanostructured with CdS and ZnS have a maximum ZTs of ~1.3 and ~1.1 at 873 K, respectively. Therefore, SnTe-based materials could be ideal alternatives for p-type lead chalcogenides for high temperature thermoelectric power generation.

Lead-free SnTe-based thermoelectrics: enhancement of thermoelectric performance by doping with Gd/Ag

“…A promising ZT of $1.1 was achieved at 873 K for our optimized sample (i.e. Ag 0.11 Gd 0.06 SnTe 0.94 Te), which is comparable to that of state-of-the-art Mg-, 25 Cd-, 10 and In -7 alloyed SnTe-based materials.…”

Role of Nanoscale Precipitates for Enhancement of Thermoelectric Properties of Heavily P-Doped Si-Ge Alloys

“…Indeed, in our samples, it has been con rmed that the nanoscale precipitates coherently or semi-coherently connect with the matrix phase, 20) and these types of matched interfaces have little in uence on the electron transport properties. [36][37][38] As can be con rmed in Fig. 4(d), the contributions of this additional scattering decrease with increasing Ge content in Si-Ge alloys.…”

Study of Anti-Tarnishing Mechanism in Ag-In Binary System by Using Semi-Quantum-Mechanical Approach

“…It could be further developed and generalized to apply to other metallic systems for noble and transition metals, since it largely correlated with the Hammer-Nørskov d-band model. It would also have potential applications in the field of valenceband engineering [67][68][69][70] for corrosion resistant alloys design. In other words, this semi-quantum-mechanical methodology is an alternative application to the HSAB principle chemical analysis in calculating, explaining, and predicting thermodynamic and reactivity behaviors for metallic materials.…”