The continued depletion of fossil fossil energy sources is leading us to a growing energy crisis. So he started looking for other resources. Thermoelectric energy conversion – a process that generates electricity from waste heat – has gained momentum as a future energy collection technology. Thermoelectric devices are used to collect heat energy through the “Seebeck effect.” The heat difference of the thermoelectric device causes the flow of charge carriers, which in turn stimulates the electrical energy.
For good conversion, a thermoelectric device must have a high conversion rate (ZT), which requires a high Seebeck coefficient (S), a high electrical conductivity (σ), and a low thermal conductivity (κ). ). The tin selenide (SnSe) is known to show a high ZT history in its single glass form. However, the activity in polycrystals is reduced due to a low σ and a high κ.
In a new study published in Advanced science, A team of researchers from Japan, led by Associate Professor Takayoshi Katase from Tokyo Institute of Technology (Tokyo Tech) tested the ZT of polycrystalline SnSe by showing a high σ and a low κ at the same time. The company achieved this amazing breakthrough by introducing tellurium (Te) ion into the form of SnSe.
It’s a catch though. The solubility of Te2- the ions in the Se2- The SnSe content is very low below the temperature equilibrium due to the difference in size between the two ions, which limits the ion exchange. The company solved this problem by using a two -step unbalanced growth process, which allowed them to increase Te.2- the binding limit is up to 0.4 in Sn (Se1-xTe told mex) large crystals.
“Adding an ion of the same valence state does not normally increase the carrier mobility of ionic semiconductors. However, in our case, it converts Te2- ion in the Se2- The site increased SnSe to the carrier’s sensitivity to three orders of magnitude, leading to a higher σ. In addition, the conversion of Te ion to κ is significantly reduced by less than a third of its value at room temperature, ”says Dr. Katase.
Two major structures achieve high σ and low κ in SnSe polycrystals. Some combine ions with another valence point, such as alkali ions, to increase the mobility of the carrier. Another is controlling the pollution separation to suppress the phonon. Therefore, there are many problems associated with the synthesis of high -performance polycrystalline SnSe.
The group, however, showed that the isovalent ion increases σ and decreases κ, at the same time. How about? The company has implemented the initial criteria for describing the machine under the ZT upgrade. The calculation of the amount of Te ion in SnSe showed that the Sn-Te chains were weak. This Sn-Te block is easily separated and a high level of Sn cavities is created in the housing, leading to a higher level of the pit. In addition, the weak Sn-Te cables reduce the phonon frequency (frequency of lattice vibration) and increase the phonon scattering, resulting in a low κ.
The study, therefore, suggests a new way to combine ions larger than their equilibrium limits, which could lead to future research on increasing the electrical properties. and heat of SnSe thermoelectric polycrystals. “We believe our insights will pave the way for high -end thermoelectric devices,” said Drs. Katase.
We hope he doesn’t get too far away.
The conversion of multiple semiconductor types enhances the thermoelectric conversion of the waste heat
Xinyi He et al, Degenerated Hole Doping and Ultra – Low Lattice Thermal Conductivity in Polycrystalline SnSe by Nonequilibrium Isovalent Te Substitution, Advanced science (2022). DOI: 10.1002 / advs.202105958
Presented by Tokyo Institute of Technology
Directions: The company achieves a 30-fold increase in thermoelectric performance on polycrystalline tin selenide (2022, March 28) retrieved on March 28, 2022 from https://phys.org/news/2022-03 -team-fold-thermoelectric-polycrystalline-tin.html
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