https://doi.org/10.1140/epjb/e2015-50594-7
Regular Article
Thermoelectrics from silicon nanoparticles: the influence of native oxide*
1
Institute for Combustion and Gas Dynamics – Reactive Fluids (IVG)
and CENIDE, University of Duisburg-Essen, Carl-Benz-Straße 199, 47057
Duisburg,
Germany
2
Faculty of Engineering and CENIDE, University of
Duisburg-Essen, Bismarckstraße
81, 47057
Duisburg,
Germany
3
KRONOS TITAN GmbH, Peschstrasse 5, 51373
Leverkusen,
Germany
a
e-mail: nils.petermann@gmx.net
Received: 2 September 2014
Received in final form: 19 January 2015
Published online: 22 June 2015
Thermoelectric materials were synthesized by current-assisted sintering of doped silicon nanoparticles produced in a microwave-plasma reactor. Due to their affinity to oxygen, the nanoparticles start to oxidize when handled in air and even a thin surface layer of native silicon oxide leads to a significant increase in the oxide volume ratio. This results in a considerable incorporation of oxygen into the sintered pellets, thus affecting the thermoelectric performance. To investigate the necessity of inert handling of the raw materials, the thermoelectric transport properties of sintered nanocrystalline silicon samples were characterized with respect to their oxygen content. An innovative method allowing a quantitative silicon oxide analysis by means of electron microscopy was applied: the contrast between areas of high and low electrical conductivity was attributed to the silicon matrix and silicon oxide precipitates, respectively. Thermoelectric characterization revealed that both, electron mobility and thermal conductivity decrease with increasing silicon oxide content. A maximum figure of merit with zT = 0.45 at 950 °C was achieved for samples with a silicon oxide mass fraction of 9.5 and 21.4% while the sample with more than 25% of oxygen clearly indicates a negative impact of the oxygen on the electron mobility.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2015
