Thermoelectric Generators Made with Novel Lead Telluride Based Materials
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Thermoelectric Generators Made with Novel Lead Telluride Based Materials Chun-I Wu a, Steven N. Girard b, Joe Sootsman b, Ed Timm c, Jennifer Nid, Robert Schmidtd, Mercouri G. Kanatzidis d,e, Harold Schock c, Eldon D. Case d, Duck Young Chunge, Timothy P. Hogana,d a
Electrical and Computer Engineering Department, Michigan State University, USA Chemistry Department, Northwestern University, USA c Mechanical Engineering Department, Michigan State University, USA d Chemical Engineering and Materials Science, Michigan State University, USA e Materials Science Division, Argonne National Laboratory, USA b
ABSTRACT For the material (Pb0.95Sn0.05Te)1-x(PbS)x nanostructuring from nucleation and growth and spinodal decomposition were reported to enhance the thermoelectric figure of merit over bulk PbTe, producing ZT of 1.1 - 1.4 at 650 K for x = 0.08[1]. Thermoelectric modules made from (Pb0.95Sn0.05Te)1-x(PbS)x materials with various hot-side metal electrodes were fabricated and tested. Short circuit current was measured on unicouples of Pb0.95Sn0.05Te – PbS 8% (ntype) legs and Ag0.9Pb9Sn9Sb0.6Te20 (p-type) legs over 10 (A) for a hot side temperature of 870K, and a cold side of 300K. Hot pressed (Pb0.95Sn0.05Te)1-x(PbS)x materials were also investigated for module fabrication. Investigations of the electrical properties of hot-pressed (Pb0.95Sn0.05Te)1x(PbS)x materials are presented along with the latest advancements in the fabrication and characteristics of modules based on the processing of these materials. INTRODUCTION The need for efficient energy conversion from heat to electricity has sparked renewed interest in solid-state power generation, such as the use of thermoelectric materials to transfer heat to electricity. The performance of thermoelectric materials is determined by its electrical and thermal properties such as electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (κ). These properties define the dimensionless thermoelectric figure of merit, ZT = S2σT/κ, where T is the temperature and S2σ is referred to as the power factor. Thermoelectric materials with high ZT are desired for fabricating a high efficiency thermoelectric module. Nanostructured thermoelectric materials have been widely studied as the materials with high ZT [2,3,4,5,6,7]. High ZT is mainly contributed by a low lattice thermal conductivity. Nanostructured Pb0.95Sn0.05Te – PbS 8% (n-type) and Ag0.9Pb9Sn9Sb0.6Te20 (p-type) materials have been found to exhibit a high figure of merit near 650K [1,7]. Further details of synthesizing and utilizing these materials to fabricate thermoelectric generators are reported in this manuscript.
EXPERIMENT MATERIAL PREPARATION Samples of Pb0.95Sn0.05Te – PbS 8% were prepared after mixing appropriate ratios of high-purity elemental starting materials (99.999% of Pb, Sn, Te, and S) and 0.055 mol % of PbI2
as an n-type dopant. The initial load was sealed in a fused silica tube under vacuum and heated to 1323 K in a rocking furnace for 12 hours. The samples were then held a
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