The lead-free tin telluride (SnTe) is considered as a potential candidate to substitute lead
telluride (PbTe) for thermoelectric power generation based on their similar crystal and
electronic structures. However, the relatively high lattice thermal conductivity and low
Seebeck coefficient of pristine SnTe are detrimental for real-life applications. This
dissertation explored elements-doping/substituting of SnTe to overcome those
shortcomings and improve SnTe thermoelectric performance.
A series of the Sn1-xGexTe phases were synthesized and studied. When the Ge amount
reaches 50% or higher, Sn1-xGexTe undergoes a phase transition from the rock-salt structure
(Fm3̅m) to the rhombohedral one (R3m). The Sn0.5Ge0.5Te phase was explored in more
details because it delivers the best thermoelectric performance with the Sn1-xGexTe series.
The electron-richer Sb and Bi were substituted on the Sn/Ge site to optimize the charge
transport properties, and Cu2Te was added into the matrix to improve the thermoelectric
performance further.
The In/Sb and In/Bi co-doping on the Sn/Ge sites was employed for Seebeck coefficient
optimization. A comparative study of the electronic structure of the Sn0.5Ge0.5Te-based
samples was performed. The calculations indicated a band convergence and changes in the
valence band, thus providing insight into the co-doping effects.
Suppression of the lattice thermal conductivity of SnTe was performed via alloying with
AgSnSe2 and PbTe, which introduced strong atomic disorder. Additionally, AgSnSe2
showed a hole donor behavior in SnTe, and the increased carrier concentration compensated for the reduction in the carrier mobility, thus rendering a decent electrical
conductivity in alloyed samples. As a result, the alloying effectively improved the samples'
thermoelectric performance. / Thesis / Doctor of Philosophy (PhD) / In recent decades, renewable energy has attracted a lot of attention due to an increase in
the global energy use and depletion of fossil fuel reserves. Thermoelectric materials are
expected to play a vital role as green energy generators to overcome the upcoming energy
crisis as they can directly convert waste heat into electricity through the Seebeck effect.
In this dissertation, the main goal is optimizing the thermoelectric performance of SnTe for
the above room temperature applications. Different doping/ substituting/alloying strategies
were applied to improve the performance. The obtained thermoelectric properties of the
SnTe-based materials were rationalized in terms of the charge carrier behavior, changes in
the electronic structure, and phonon propagation.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/28461 |
| Date | January 2023 |
| Creators | Song, Shaochang |
| Contributors | Mozharivskyj, Yurij, Chemistry |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.0016 seconds