Skutterudites for Thermoelectric Applications: Properties, Synthesis and Modelling
Résumé
Skutterudites are a class of compounds promising in thermoelectric field.
They are among the most studied thermoelectric materials of the last decade because related to the concept of electron-phonon-glass crystal. In literature there are many studies on Co-based skutterudites filled with Rare Earths (RE) (Ballikaya et al. 2012, Daniel et al. 2015, Zhang et al. 2015, Lili et al. 2015, Bhaskar et al. 2015) and Fe,Co-based (REFe4 -xCoxSb12) (Jacobsen et al. 2014, Zhang et al. 2015, Rogl et al. 2010a), while very few are the studies on Fe,Ni–based skutterudites (REFe4-xNixSb12) (Tan et al. 2013a, Kaltzoglou et al. 2012, Morimura et al. 2003).
The name “Skutterudite” comes from a small mining town, Skutterud, in Norway where it was extracted and classified for the first time in 1845. The natural Skutterudite is a cobalt arsenide mineral that contains variable amounts of Ni and Fe, substituting for cobalt, having the general formula: (Co,Ni,Fe)As3. Its orogeny is hydrothermal, in moderate-high temperature; it is often found associated with other minerals such as Arsenopyrite, native Silver, Erythrite, Annabergite, Nickeline, Cobaltite, Silver sulfosalts, native Bismuth, Calcite, Siderite, Barite and Quartz. Its density is about 6.5 g/cm3 and the Mohs hardness is 6 but these values strictly depend on the composition.
Synthetic skutterudites are now produced in laboratory. They include compounds having the composition MX3, where M is a transition metal of the VIII, IX, X group and X represents a pnitogen atom belonging to the XV group. Oftedal in 1928 identified CoAs3 as the first synthetic skutterudites and determined its structure as a cubic body-centered cell and space group . CoAs3 is now reported as the prototype compound for skutterudites.
The modelling of skutterudite properties has been the subject of a large number of publications over the past decades. In this review we will only consider a limited set of results pertaining to Fe- or Ni-based skutterudites. This choice aims at preserving coherence with the experimental section of this chapter that mainly deals with these types of compounds.
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