日本金属学会誌

J. Japan Inst. Met. Mater, Vol. 79, No. 11 (2015),
pp. 562-568

Crystal Structure and Thermoelectric Properties of Ge-Sb-Te Homologous Structure

Atsuko Kosuga1, Hiroki Ishibashi2, Yoshiki Kubota2 and Kouichi Kifune3

1Nanoscience and Nanotechnology Research Center, Research Organization for the 21st Century, Osaka Prefecture University, Sakai 599-8570
2Graduate School of Science, Osaka Prefecture University, Sakai 599-8531
3Faculty of Engineering, Hiroshima Institute of Technology, Hiroshima 731-5193

Abstract:

We studied the effects of different preparation method and In-substitution on its crystal structure and thermoelectric (TE) properties of polycrystalline GeSb6Te10. Firstly, the effects of spark plasma sintering (SPS) on the crystal structure and elemental distribution of GeSb6Te10 were discussed. GeSb6Te10 consolidated using SPS consisted of a mixture of GeSb6Te10-type homologous and Sb2Te3-type tetradymite structures, whereas the sample prepared by melting had a single homologous structure. The elemental compositional deviation from the nominal composition of the sample prepared by SPS was wider than that prepared by melting. This implies that SPS promoted atomic diffusion and rearrangement of elements, leading to a substantial change in the crystal structure and elemental distribution of GeSb6Te10. Secondly, the effects of In-substitution on the crystal structure and TE properties of GeInxSb6-xTe10 (x=0, 0.18, 0.3, and 0.6) prepared by melting were discussed. Rietveld and Le Bail analyses showed that all compositions crystallized in trigonal structures with a 51-layer period. Substituting In decreased both the lattice and electronic thermal conductivity, as well as markedly increased the Seebeck coefficient. We ascribed this increase to increases in the effective mass of the carriers, likely caused by the formation of additional energy states near the Fermi level. In GeIn0.6Sb5.4Te10, we found a maximum dimensionless figure of merit: ZTmax of 0.75 at 710 K, 1.9 times higher than that of GeSb6Te10.

[doi:10.2320/jinstmet.JA201506]


(Received 2015/5/1)

Keywords:

thermoelectric, homologous, crystal structure, electrical property, thermal conductivity


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