Configuring pnicogen rings in skutterudites for low phonon conductivity
- Configuring pnicogen rings in skutterudites for low phonon conductivity
- Hang Chi; 김형철; John C. Thomas; Xianli Su; Stephen Stackhouse; Massoud Kaviany; Anton Van der Ven; Xinfeng Tang; Ctirad Uher
- Thermoelectrics; Skutterudites; Thermal conductivity; Lattice dynamics; Phase diagram
- Issue Date
- Physical review B, Condensed matter and materials physics
- VOL 86, NO 19, 195209-1-195209-7
- Dominant heat-carrying modes in skutterudites are associated with vibrations of the pnicogen rings. Apart from
filling the structural cages with foreign species, disrupting the pnicogen ring structure by substitutional alloying
should be an effective approach to reduce thermal conductivity. In this paper we explore alloying configurations
of pnicogen rings (Sb rings in the case of CoSb3) that yield particularly low values of the thermal conductivity.
We find that IV-VI double substitution (replacing two Sb atoms with one atom each from the column IV and
column VI elements to achieve an average charge of two Sb atoms) is a very effective approach. Our ab initio
calculations, in combination with a cluster expansion, have allowed us to identify stable alloy configurations
on the Sb rings. Subsequent molecular and lattice dynamics simulations on low energy configurations establish
the range of atomic displacement parameters and values of the thermal conductivity. Theoretical results are in
good agreement with our experimental thermal conductivity values. Combining both approaches of compensated
double substitution and filling of structural cages should be an effective way of improving the thermoelectric
figure of merit of skutterudites.
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