| About this Abstract |
| Meeting |
2011 Electronic Materials Conference
|
| Symposium
|
2011 Electronic Materials Conference
|
| Presentation Title |
B3, The Impact of Nano-Inclusions Introduced by Mechanical Alloying on Thermoelectric Transport in Pb1-xSnxTe: Experimental Results and Theoretical Predictions |
| Author(s) |
Lakshmi Krishna |
| On-Site Speaker (Planned) |
Lakshmi Krishna |
| Abstract Scope |
In this work we analyze experimentally measured electrical conductivity data and Seebeck coefficient data measured from 300 K to 700 K from two n-type Pb<SUB>1-x</SUB>Sn<SUB>x</SUB>Te samples (1.2x10<SUP>19</SUP>/cm<SUP>3</SUP> and 3.8x10<SUP>18</SUP>/cm<SUP>3</SUP>) made by mechanical alloying with differing amounts of Sn (x=0.066 and 0.269, respectively) . It is determined by X-ray diffraction analysis that approximately 2 vol.% of both alloys are ~15nm diameter SnO<SUB>2</SUB> inclusions. To analyze the impact of the secondary phase inclusions on Pb<SUB>1-x</SUB>Sn<SUB>x</SUB>Te alloys we first compare the experimental data to a three-band model of what would be predicted[1] if electron scattering were to be dominated by just phonons and alloy scattering. For both alloys, the experimentally measured mobility is much smaller than what would be expected near room temperature, but is close to the calculated phonon-dominated mobility at higher temperatures. However, the magnitude of the experimentally measured Seebeck coefficient is significantly larger over the entire temperature range than what would be expected if phonon and alloy scattering were to dominate. The impact of electron scattering by nano-inclusions can be modeled in the framework of the Boltzmann transport equation using the relaxation time approximation. A scattering term with a E<SUP>3/2 </SUP> relaxation time energy dependence has been proposed by Faleev, et.al.[2] to be appropriate. When this term is incorporated into the theoretical calculations, it is found that the calculations agree with the experimentally measured conductivity data and Seebeck coefficient data over the entire temperature range investigated. We conclude that the ~ 15 nm diameter SnO<SUB>2</SUB> inclusions present in mechanically alloyed Pb<SUB>1-x</SUB>Sn<SUB>x</SUB>Te increase the magnitude of the Seebeck coefficient due to an energy filtering effect that is consistent with the expected E<SUP>3/2 </SUP> dependence of the relaxation time characterizing their contribution to electron scattering. The impact of this on the material’s thermoelectric figure of merit as a function of temperature will be discussed. |
| Proceedings Inclusion? |
Undecided |