Abstract
The thermoelectric half-Heusler compounds Ti x NiSn0.998Sb0.002 (x = 1.0 to 1.2) and Ti y Zr0.25Hf0.25NiSn0.998Sb0.002 (y = 0.5 to 0.65) with nonstoichiometric nominal compositions were prepared by spin-casting and subsequent annealing at 1073 K for 24 h. The dimensionless figure of merit ZT at room temperature was maximized at x = 1.1 and y = 0.6 in Ti-rich compounds through an increase in absolute Seebeck coefficients despite a decrease in electrical conductivities. ZT reached 0.07 at x = 1.1 and 0.14 at y = 0.6. In powder x-ray diffraction analysis, minor phases of β-Sn, TiNi, Ti2Sn, and Ti5Sn3 were observed in addition to a major phase of half-Heusler. The quantity of the minor phases was minimized at x = 1.1 and y = 0.55, where the absolute Seebeck coefficients are maximized. In transmission electron microscopic (TEM) analysis of Ti0.55Zr0.25Hf0.25NiSn0.998Sb0.002, crystal grains of the half-Heusler phase, from several hundred nanometers to several micrometers in size, were observed. TEM energy-dispersive spectroscopy measurements indicated that fluctuations of Ti, Zr, and Hf compositions within the Ti-site in the half-Heusler phase may occur. Thermoelectric properties were improved at x = 1.1 and y = 0.6 rather than at the stoichiometric compositions of x = 1.0 and y = 0.5 due to minimization of the precipitate quantities.
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References
C. Uher, J. Yang, S. Hu, D.T. Morelli, and G.P. Meisner, Phys. Rev. B 59, 8615 (1999).
N. Shutoh and S. Sakurai, J. Alloys Compd. 389, 204 (2005).
Q. Shen, L. Chen, T. Goto, T. Hirai, J. Yang, G.P. Meisner, and C. Uher, Appl. Phys. Lett. 79, 4165 (2001).
Q. Shen, L. Zhang, L. Chen, T. Goto, and T. Hirai, J. Mater. Sci. Lett. 20, 2197 (2001).
T. Morimura, M. Hasaka, S. Yoshida, and H. Nakashima, J. Electron. Mater. 38, 1154 (2009).
F. Izumi and T. Ikeda, Mater. Sci. Forum 321–324, 198 (2000).
R. Venkatasubramanian, E. Siivola, T. Colpitts, and B. O’Quinn, Nature 413, 597 (2001).
R.V. Skolozdra, Y.V. Stadnyk, Y.K. Gorelenko, and E.É. Teletskaya, Sov. Phys. Solid State 32, 1536 (1990).
T. Nobata, G. Nakamoto, M. Kurisu, Y. Makihara, T. Tokuyoshi, and I. Nakai, Jpn. J. Appl. Phys. 38, 429 (1999).
T. Nobata, G. Nakamoto, M. Kurisu, Y. Makihara, K. Ohoyama, and M. Ohashi, J. Alloys Compd. 347, 86 (2002).
T. Morimura and M. Hasaka, Ultramicroscopy 106, 553 (2006).
T. Morimura, M. Hasaka, and S. Kondo, Scr. Mater. 59, 886 (2008).
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Morimura, T., Hasaka, M., Shimoda, K. et al. Microstructures of Annealed TiNiSn-Based Alloy Ribbons. J. Electron. Mater. 39, 2149–2153 (2010). https://doi.org/10.1007/s11664-009-0982-1
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DOI: https://doi.org/10.1007/s11664-009-0982-1