Investigation of Thermoelectric Materials: Substitution effect of Bi on the Ag 1-x Pb 18 MTe 20 (M = Sb, Bi) (x = 0, 0.1
- PDF / 227,479 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 105 Downloads / 249 Views
1044-U03-14
Investigation of Thermoelectric Materials: Substitution effect of Bi on the Ag1-xPb18MTe20 (M = Sb, Bi) (x = 0, 0.14, 0.3) Mi-kyung Han1, Huijun Kong2, Ctirad Uher2, and Mercouri G Kanatzidis1 1 Department of Chemistry, Northwestern University, Evanston, IL, 60208 2 Department of Physics, University of Michigan, Ann Arbor, MI, 48109 ABSTRACT We performed comparative investigations of the Ag1-xPb18MTe20 (M = Bi, Sb) (x = 0, 0.14, 0.3) system to better understand the roles of Sb and Bi on the thermoelectric properties. In both systems, the electrical conductivity nearly keeps the same values, while the Seebeck coefficient decreases dramatically in going from Sb to Bi. Compared to the lattice thermal conductivity of PbTe, that of AgPb18BiTe20 is substantially reduced. The lattice thermal conductivity of the Bi analog, however, is higher than that of AgPb18SbTe20 and this is attributed largely to the decrease in the degree of mass fluctuation between the nanostructures and the matrix (for the Bi analog). As a result the dimensionless figure of merit ZT of Ag1xPb18MTe20 (M = Bi) is found to be smaller than that of Ag1-xPb18MTe20 (M = Sb). INTRODUCTION Thermoelectric materials have been the subject of intensive investigations and can be used for converting heat directly into electricity or for cooling application.[1-2] The performance of a thermoelectric material is assessed with the figure of merit ZT defined as (S2σ/κ)T; where S is the Seebeck coefficient (or thermopower), σ electrical conductivity, κ thermal conductivity, and T is the temperature. High performance thermoelectric materials require large Seebeck coefficient and electrical conductivity and low thermal conductivity. A variety of materials in the form of thin film or bulk samples have been studied with respect to their thermoelectric properties and significant progress has been achieved in increasing ZT. [3-5] Recently, we reported
that the Ag1-xPb18SbTe20 (LAST-18) system can achieve an impressively high figure of merit. (ZT ~1.7 at 700K for AgPb18SbTe20).[6] Subsequently, we reported other similar quaternary systems with ZT > 1.5.[7-9] In this work we performed a comparative investigation of the Ag1-xPb18MTe20 (M = Bi, Sb) (x = 0, 0.14, 0.3) system to assess the roles of Sb and Bi on the thermoelectric properties. Namely, the series of Ag1-xPb18BiTe20 (x = 0, 0.14, 0.3) samples was investigated and compared with a corresponding series of Ag1-xPb18SbTe20 (x = 0, 0.14, 0.3) (LAST-18) compositions prepared under the same conditions as the Bi analogs. We show that the proper combination of metals is essential in obtaining enhanced thermoelectric properties in PbTe derive materials and the nature of the trivalent element is in fact critical in affecting the transport properties. Sb seems to play a key role in enhancing the thermoelectric properties of LAST. How Sb is superior to Bi in imparting the system significantly higher ZT is explored and discussed herein. EXPERIMENTAL SECTION Ag1-xPb18MTe20 (M = Bi, Sb) (x = 0, 0.14, 0.3) samples were synt
Data Loading...
