Study of Chevrel phases for thermoelectric applications: band structure calculations on compounds (M = metal)

Abstract

Chevrel phases, , present large voids in their lattice, where cations can be inserted. These cations are weakly bound and constitute good scattering centres for phonons. The lattice thermal conductivity of these compounds must be very low, and these phases are then good candidates for thermoelectric application. But most of them are metallic and superconducting. Some band structure calculations have been performed in order to find a semiconducting one. and are found to be metallic and semiconducting.

Preparation and Thermoelectric Properties of Chevrel-Phase Cu<I><SUB>x</SUB></I>Mo<SUB>6</SUB>S<SUB>8</SUB> (2.0&le;<I>x</I>&le;4.0)

“…Band structure calculations have been carried out for several Chevrel-phase selenides for predicting their thermoelectric properties. 11,13,14,17,24) The results suggest that CrMo 11,13,14,17) Moreover, the results imply that the Fermi level of TiMo 6 Se 8Ày shifts to the valence band edge when the Se content decreases. 24) Therefore, the thermoelectric properties of Chevrel phases would be improved by altering their chemical compositions.…”

“…[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Most of the previous studies on Chevrel phases have focused on Chevrel-phase selenides. Band structure calculations have been carried out for several Chevrel-phase selenides for predicting their thermoelectric properties.…”

Thermoelectric Properties of Chevrel-Phase Sulfides M x Mo6S8 (M: Cr, Mn, Fe, Ni)

“…Further, several studies have attempted to predict the thermoelectric properties of some Chevrel-phase selenides by bandstructure calculations. 2,4,5,8,15 Results of these studies suggest that triclinic TiMo 6 Se 8 , hexagonal Zn 2 Mo 6 Se 8 , and hexagonal Cd 2 Mo 6 Se 8 are expected to exhibit good thermoelectric properties. Since oxidation states of 4+ for Ti and 2+ for Zn and Cd are assumed, these Chevrel-phase selenides have the same cluster-VEC of 4.0.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The host structure of a Chevrel phase consists of stacked Mo 6 X 8 clusters. [20][21][22] Metal cations fill the space between the Mo 6 X 8 clusters.…”

“…[1][2][3][4][5][7][8][9][10][14][15][16][17] For example, Caillat et al 7 reported that Cu 1.38 Fe 0.66 Mo 6 Se 8 with a hexagonal structure has a ZT value of 0.6 at 1150 K. Since oxidation states of 1+ for Cu and 2+ for Fe are assumed, the cluster-VEC of Cu 1.38 Fe 0.66 Mo 6 Se 8 is 3.8. Further, several studies have attempted to predict the thermoelectric properties of some Chevrel-phase selenides by bandstructure calculations.…”