Preparation and evaluation of the n-type PbTe based material properties for thermoelectric generators
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Preparation and evaluation of the n-type PbTe based material properties for thermoelectric generators Tse-Hsiao Li1, Jenn-Dong Hwang1, Hsu-Shen Chu1, Chun-Mu Chen1, Chia-Chan Hsu1, Chien-Neng Liao2, Hsiu-Ying Chung3, Tsai-Kun Huang4, Jing-Yi Huang4, Huey-Lin Hsieh4 1
Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan, ROC. Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan, ROC. 3 Materials Science and Engineering, Feng chia University, Taichung, Taiwan, ROC. 4 China Steel Corporation, Taiwan, ROC. 2
ABSTRACT Owing to energy conservation of waste heat, Lead telluride, PbTe, based materials have promising good thermoelectric properties around a range of middle temperature (Fig. 1, from 300 to 600ɗ), due to their high melting point, fine chemical stability, and the high figure of merit Z. The general physical properties and factors affecting the figure of merit have been reviewed. This research is focused on the n-type of PbTe materials and collocated with analysis of densities, hardness, elastic modulus, and thermoelectric properties thermoelectric figure of merit ZT=GS2T/κ (where G is electrical conductivity, S is Seebeck coefficient , T is absolute temperature, and κ is thermal conductivity). Room temperature hardness and Young’s modulus are measured by nano-indentation. In this study, the hot-press compacts under the pressure of 4 ton/cm2 can reach the maximum density about 8.2 g/cm3, and hardness and elastic modulus are 0.6 GPa and 70 GPa, respectively. The figure of merit value (ZT) of PbTe in low temperature (around 340ɗ) was found about 1 with carrier concentration above 1019 cm-3. These results also indicate that the powder metallurgy parameters provide potentialities for further increase of the high efficiency of energy conversion in PbTe materials.
Fig.1 Performance of the established thermoelectric materials
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Introduction In general, thermoelectric effect is scientific and technological interest due to its widely application possibilities especially in power saving. Recent developments in theoretical studies on the thermoelectric effects, as well as the newly discovered thermoelectric materials provide new opportunities for wide applications[1-3]. There were great efforts to explore more effective materials, especially in semi-conductors. The theory identified at that time that the figure of merit for thermoelectric application is ZT= TS2G/κ, where T is absolute temperature, S is the Seebeck coefficient, G is the electric conductivity, and κ is the thermal conductivity. High ZT thermoelectric materials should be large S, high G, low κ, and could be found in semiconductor materials with carrier concentration of about 1019 cm-3. One type of these materials, PbTe is based on the strongly correlated electron systems, and it also has ionic covalent bond with cubic sodium chloride-type lattice. The high ZT is also attributed to the doping, and introducing a strong enhancement of the density of states (DOS) due to a resona
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