Thermoelectric materials filled skutterudites

The transition-metal monopnictides MPn with the MnP-type structure discussed above contain strong M-M and weak Pn-Pn bonds. Compounds richer in Pn can also be examined by XPS, such as the binary skutterudites MPn , (M = Co, Rh, Ir Pn = P, As, Sb), which contain strong Pn-Pn bonds but no M-M bonds [79,80], The cubic crystal structure consists of a network of comer-sharing M-centred octa-hedra, which are tilted to form nearly square Pnn rings creating large dodecahedral voids [81]. These voids can be filled with rare-earth atoms to form ternary variants REM Pnn (RE = rare earth M = Fe, Ru, Os Pn = P, As, Sb) (Fig. 26) [81,82], the antimonides being of interest as thermoelectric materials [83]. 

I lcurial et al., 1996). This discovery greatly increased the interest in these materials for thermoelectric applications. In addition to the stoichiometric filled skutterudite compounds of the form RM4X12, a large number of related alloys were also investigated as possible thermoelectric materials. Most of the research on lanthanide skutterudites in the context of thermoelectric applications has been reviewed recently by Uher (2001), Nolas et al. (1999), and Sales (1998) and hence only a brief summary of the thermoelectric research will be highlighted in this section. 

Fig. 23. ZT vs. T for several state-of-the-art thermoelectric materials and for a filled skutterudite with x 1. (Figure from T.M. Tritt, unpublished.)...

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