Hostname: page-component-848d4c4894-m9kch Total loading time: 0 Render date: 2024-05-16T23:32:27.344Z Has data issue: false hasContentIssue false
  • English
  • Français

Crystal Structure and Thermoelectric Properties of Mn-Substituted Ru2Si3 with the Chimney-Ladder Structure

Published online by Cambridge University Press:  01 February 2011

Tatsuya Koyama ,
Norihiko L. Okamoto ,
Kyosuke Kishida ,
Katsushi Tanaka  and
Haruyuki Inui
Tatsuya Koyama
Affiliation:
tako@tsuya.mbox.media.kyoto-u.ac.jp, Kyoto University, Materials Science and Engineering, Kyoto, Japan
Norihiko L. Okamoto
Affiliation:
n.okamoto@at4.ecs.kyoto-u.ac.jp, Kyoto University, Materials Science and Engineering, Kyoto, Japan
Kyosuke Kishida
Affiliation:
k.kishida@materials.mbox.media.kyoto-u.ac.jp, Kyoto University, Materials Science and Engineering, Kyoto, Japan
Katsushi Tanaka
Affiliation:
k.tanaka@materials.mbox.media.kyoto-u.ac.jp, Kyoto University, Department of Materials Science and Engineering, Kyoto, Japan
Haruyuki Inui
Affiliation:
haruyuki.inui@materials.mbox.media.kyoto-u.ac.jp, Kyoto University, Materials Science and Engineering, Kyoto, Japan
Get access

Abstract

Chimney-ladder compounds with the general chemical formula of Mn X2n-m (n, m: integers) possess tetragonal crystal structures which consist of two types of subcells; one composed of transition metal atoms (M) with the γÀ-Sn structure and the other composed of group 13 or 14 atoms (X) with a helical arrangement along the tetragonal c-axis. Since the chimney-ladder compounds generally exhibit very low thermal conductivity, presumably due to its long periodicity along the c-axis, they have been extensively investigated as promising thermoelectric materials. The high-temperature (HT) phase of Ru2Si3 is one of the chimney-ladder compounds with n=2 and m=1. Recently we have found that the HT-Ru2Si3 phase is stabilized by substituting Ru with Re so as to exist even at low temperatures in a wide compositional range of the Re content (Re: 14 to 73%), and that the thermoelectric power factor for alloys with high Re contents increases with the Re content and the highest value was obtained for the alloy with the highest Re content (73%), which is the solubility limit of Re in the chimney-ladder phase. In order to further enhance the thermoelectric properties, another ternary element which extends the solid solubility region of the HT-Ru2Si3 phase is favorable. We have chosen Mn as the ternary element because Mn4Si7 with the chimney-ladder structure exists as a counterpart of HT-Ru2Si3 in the Ru2Si3 -Mn4Si7 pseudo-binary system so that the solid solubility region of the chimney-ladder phase is anticipated to extend in a wider composition range than the Re case. Our study, in fact, shows that the Mn-substitution stabilizes the HT-Ru2Si3 phase in a wide compositional range of the Mn content; 12 to 100%. Compositional analyses indicate that the Si/M ratio gradually increases as the Mn content increases. This is considered to be due to the addition of Si atoms in the Si subcell in order to compensate the decrease in the valence electron concentrations (VEC) per M atom by the substitution of Ru (group 8) with Mn (group 7) with fewer valence electrons. The Seebeck coefficient and electrical resistivity of the Mn-substituted Ru2Si3 are explained in terms of the VEC deviation from the idealized value, 14, which is expected for intrinsic semiconductors with the chimney-ladder structure. The highest dimensionless thermoelectric figure of merit (ZT=0.76) is obtained for 90%Mn-substituted alloy. The relationships between the microstructure and thermoelectric properties will be discussed.

Keywords

transmission electron microscopy (TEM)thermoelectricitycrystallographic structure
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1128: Symposium U – Advanced Intermetallic-Based Alloys for Extreme Environment and Energy Applications , 2008 , 1128-U05-01
Copyright
Copyright © Materials Research Society 2009

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Poutcharovsky, D. J., Yvon, K. and Parthé, E., J. Less-Common Met. 40, 139 (1975).Google Scholar
2. Susz, C. P., Muller, J., Yvon, K. and Parthé, E., J. Less-Common Met. 71, P1 (1980).Google Scholar
3. Simkin, B. A., Hayashi, Y. and Inui, H., Intermetallics, 13, 1225 (2005).Google Scholar
4. Ivanenko, L., Filonov, A., Shaposhnikov, B., Behr, G., Souptel, D., Schumann, J., Vinzelberg, H., Plotnikov, A. and Borisenko, V., Microelectronic Eng. 70, 209–214 (2003).Google Scholar
5. Zaitsev, V. K., Thermoelectric properties of anisotropic MnSi1.75 , in CRC handbook on thermoelectrics, edited by Rowe, D. M. (CRC Press, New York, 1994), pp. 299–309.Google Scholar
6. Nowotny, H., The chemistry of extended defects in non-metallic solids, edited by Eyring, E. R. and O'Keefe, M. (Amsterdam, North-Holland, 1970), p 223.Google Scholar
7. Ye, H. Q. and Amelinckx, S., J. Solid State Chem. 61, 8 (1986).Google Scholar
8. Simkin, B. A., Ishida, A., Okamoto, N. L., Kishida, K., Tanaka, K. and Inui, H., Acta Mater. 54, 2857 (2006).Google Scholar
9. Ishida, A., Okamoto, N. L., Kishida, K., Tanaka, K. and Inui, H., Mater. Res. Soc. Symp. Proc. 980, II05–37 (2007).Google Scholar
10. Kishida, K., Ishida, A., Koyama, T., Harada, S., Okamoto, N. L., Tanaka, K. and Inui, H., Acta Mater.[submitted].Google Scholar