Chevrel Phases as Good Thermoelectric Materials

Abstract

Chevrel phases have an open lattice with large voids in which cations can be inserted. These cations are good scattering centers for phonons. The thermal conductivity of these compounds must be low. Chevrel phases are generally metallic, but we calculated the density of states of several compounds and we found that Zn2Mo6Se8, Cd2Mo6Se8, TiMo6Se8 are semiconducting whereas SnMo6Se8, Cu2Mo6Se8 and CrMo6Se8 are metallic. We are currently trying to synthesize Zn2Mo6Se8 by different ways.

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)

“…[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.…”

“…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.…”