Synchrotron-radiation X-raypowder diffraction study of alpha- and beta-Zn4Sb3compounds
T. Souma1,G. Nakamoto1, M. Kurisu1, K. Kato2, M. Takata2,3
1Japan Advanced Institute ofScience and Technology, Tatsunokuchi, Ishikawa 923-1292, Japan
2Japan Synchrotron RadiationResearch Institute/SPring-8, Hyogo 679-5198, Japan
3Department of Applied Physics,Nagoya University, Nagoya 464-8603, Japan
Beta-Zn4Sb3compound has been recently identified as a new thermoelectric material withhigh figure of merit of ZT=1.4 at 670 K. However, there have been few thermoelectricdata on the low-temperature alpha-phase, which is stable below 263 K.Furthermore, the crystal structure of the alpha-Zn4Sb3and the details of the structural phase transition from the alpha- tobeta-phase have not been reported yet. In this study, we have investigated thecrystal structures of the alpha- and beta-Zn4Sb3 by anX-ray powder diffraction in the temperature range of 180 to 295 K. Thesynchrotron-radiation X-ray powder experiments have been performed at theSPring-8 BL02B2 station. The diffraction patterns of Zn4Sb3have been refined by the Rietveld profile fitting program RIETAN-2000. All thediffraction peaks of the alpha-Zn4Sb3 at 180 K areindexed by assuming a rhombohedral structure with the space group of R-3c as in the beta-Zn4Sb3.A drastic increase in the c/ais observed at the structural phase transition temperature from the alpha- tobeta-phase. The refined structure parameters are determined for both the alpha-and beta-Zn4Sb3.