Half-Heusler Thermoelectrics

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• Dr. Jan-Willem Bos, Institute of Chemical Sciences, Heriot-Watt University
• Friday 25 October 2013, 13:45-15:00
• Physics East 217.

If you have a question about this talk, please contact Elizabeth Blackburn.

Thermoelectric materials afford reliable and compact electrical power generators without any moving parts that can operate on various sources of heat. In particular, they can be used to generate power from the waste heat of other power generators, such as combustion engines. Materials with the half-Heusler structure are promising thermoelectric materials because they combine large Seebeck coefficients (S) and high electrical conductivities (sigma), which is a key requirement for good thermoelectric performance. Unfortunately, the overall efficiency remains modest due to a large thermal conductivity (kappa), which limits the thermoelectric figure of merit, ZT = (S^2 sigma / kappa)T  1.

Our research has so far focused on the promising n-type XNiSn materials where X = Ti, Zr or Hf. The main results are as follows: Firstly, we have established that samples containing a mixture of X-metals form as a composite of many discrete half-Heusler compositions [1]. Interestingly, this does not have an adverse effect on the thermoelectric performance. Secondly, we have discovered that the electronic properties can be modified by introducing interstitial transition metal dopants [2,3]. This has not been explored before and offers a new route to control the thermoelectric performance. These new contributions to the fundamental understanding of the half-Heusler thermoelectric materials will be discussed during the seminar.

[1] R. A. Downie, D. A. MacLaren and J. W. G. Bos, Submitted to J. Mater. Chem.

[2] R. A. Downie, D. A. MacLaren, R. I. Smith and J. W. G. Bos, Chem. Commun., 2013, 49, 4184.

[3] R. A. Downie, D. A. MacLaren, R. I. Smith and J. W. G. Bos, in preparation.

This talk is part of the Condensed Matter Physics Seminars series.

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