ICT2014 Abstracts

This paper focuses on the thermoelectric properties of complex structure borides, β-rhombohedral boron (β-boron) and new ternary Ti₁₀Ru₁₉B₈ compounds. Traditionally, β-boron is recognized as a high temperature thermoelectric material operated above 1300 K. So far, the highest ZT of 0.30 was achieved at 1700 K by Slack et al. [1]. In addition, several attempts to improve the thermoelectric properties in β-boron through element doping were performed by Kim et al. [2,3]. Among various dopants, V-doping can enhance ZT from 0.002 up to 0.01 at 885 K, that is comparable to that of p-type B₄C compound [2,3].

One of the presenting topics is further power factor enhancement by Cu-doping for β-boron. Although 1.0 at.% Cu doping effect on the thermoelectric properties have been investigated [1,3], we found that further Cu-doping (> 1.0 at.%) would enhance them significantly. To clarify the origin of power factor enhancement, we will discuss structural information such as site occupancies with varying Cu concentration determined by Rietveld refinement.

The other one is about a new ternary compound Ti₁₀Ru₁₉B₈ [4]. This new compound forms a pseudogap near the Fermi level, as confirmed by band structure calculation. We synthesized a single phase of Ti₁₀Ru₁₉B₈ by arc-melting and spark plasma sintering technique, and found that undoped Ti₁₀Ru₁₉B₈ exhibited ZT = 0.12 at 973 K. This value would be enhanced by tuning carrier concentration. Furthermore, the possibility for further ZT enhancement from theoretical perspective will be given in this presentation.

References

[1] G. A. Slack et al., Proc. 9^th Int. Symp. on Boron, Borides, and Related Compounds, ed. By H. Werheit, 132 (1987).

[2] H. K. Kim et al., Mater. Trans. 49, 593 (2008).

[3] H. K. Kim and K. Kimura, Mater. Trans. 52, 41 (2011).

[4] B. P. T. Fokwa, Z. Anorg. Allg. Chem. 635, 2258 (2009).