The effect of phase heterogeneity on thermoelectric properties of nanostructured silicon germanium alloy

Detailed examination of the nanostructured bulk Si0.80Ge0.20 alloy synthesized by mechanical alloying and hot-press methods revealed that the alloy composition can unintentionally deviate from its nominal value. The phase deviation is difficult to be detected with x-ray diffraction due to the contin...

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Veröffentlicht in:Journal of applied physics 2013-07, Vol.114 (2)
Hauptverfasser: Zamanipour, Zahra, Salahinejad, Erfan, Norouzzadeh, Payam, Krasinski, Jerzy S., Tayebi, Lobat, Vashaee, Daryoosh
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Sprache:eng
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Zusammenfassung:Detailed examination of the nanostructured bulk Si0.80Ge0.20 alloy synthesized by mechanical alloying and hot-press methods revealed that the alloy composition can unintentionally deviate from its nominal value. The phase deviation is difficult to be detected with x-ray diffraction due to the continuous solid solution characteristics of the Si-Ge alloy. Differential thermal analysis, in particular, showed that the synthesized nanostructured bulk Si0.80Ge0.20 alloy was a composition of two unintentional phases. The dominant phase was Si0.88Ge0.12 with admixture of Si0.58Ge0.42 in a much lower concentration. The two-phase structure is difficult to be detected in X-ray diffraction analysis and is often neglected. Thermoelectric properties of Si1−xGex significantly depend on the Ge content in the synthesized alloy. The thermoelectric properties of the synthesized material were studied experimentally and theoretically. The comparison of the data of the mixed phase nanostructured alloy with those of the single phase Si0.80Ge0.20 alloy showed enhancement in Seebeck coefficient and reduction in thermal conductivity of the former material. It was found using model calculations that these differences are due to the existence of the Si0.88Ge0.12 phase in the two-phase structure that results in the reduction of the bipolar diffusion part of the thermal conductivity and the bipolar effect in the Seebeck coefficient at high temperature. The results can stimulate a new route for enhancing the thermoelectric properties of silicon germanium alloy based on multicomponent material design.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4813474