Boundary Scattering and the Thermoelectric Figure of Merit

✍ Scribed by Sharp, J.W. ;Poon, S.J. ;Goldsmid, H.J.

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 124 KB
• Volume: 187
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/1521-396x(200110)187:2<507::aid-pssa507>3.0.co;2-m

✦ Synopsis

The lattice thermal conductivity of a thermoelectric material can be significantly reduced at ordinary temperatures by boundary scattering but the beneficial effect on the figure of merit can sometimes be more than offset by boundary scattering of the charge carriers. Here we extend the previous theory to include both weak and strong boundary scattering. We show that the relative magnitudes of the effects on the phonons and charge carriers can be estimated and illustrate our predictions by applying them to Si-Ge alloys, Bi-Sb alloys, and Bi 2 Te 3 alloys. Our theory does not distinguish between the effects of acoustic and optical phonons and may, therefore, be criticized when applied to materials with large unit cells. We present an alternative treatment for this case using a classical method for assessing the thermal conductivity due to the acoustic phonons. The new technique is applied to one of the half-Heusler alloys, Zr 0.5 Hf 0.5 NiSn.