期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：11
页码：3269-3274
DOI：10.1073/pnas.1424388112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThermoelectric materials have been extensively studied for applications in conversion of waste heat into electricity. The efficiency is related to the figure-of-merit, ZT = (S2{sigma}/{kappa})T, where S,{sigma} , and{kappa} are the Seebeck coefficient, electrical conductivity, and thermal conductivity, respectively. Pursuing higher ZT for higher efficiency has been the focus by mainly reducing the thermal conductivity. In this paper, we point out, for a given ZT, higher power factor (S2{sigma}) should be pursued for achieving more power because power is determined by (Th - Tc)2(S2{sigma})/L, where Th, Tc, and L are the hot and cold side temperatures, and leg length, respectively. We found a new material, Mg2Sn0.75Ge0.25, having both high ZT and high power factor. Thermoelectric power generation is one of the most promising techniques to use the huge amount of waste heat and solar energy. Traditionally, high thermoelectric figure-of-merit, ZT, has been the only parameter pursued for high conversion efficiency. Here, we emphasize that a high power factor (PF) is equivalently important for high power generation, in addition to high efficiency. A new n-type Mg2Sn-based material, Mg2Sn0.75Ge0.25, is a good example to meet the dual requirements in efficiency and output power. It was found that Mg2Sn0.75Ge0.25 has an average ZT of 0.9 and PF of 52 W*cm-1*K-2 over the temperature range of 25-450 {degrees}C, a peak ZT of 1.4 at 450 {degrees}C, and peak PF of 55 W*cm-1*K-2 at 350 {degrees}C. By using the energy balance of one-dimensional heat flow equation, leg efficiency and output power were calculated with Th = 400 {degrees}C and Tc = 50 {degrees}C to be of 10.5% and 6.6 W*cm-2 under a temperature gradient of 150 {degrees}C*mm-1, respectively.
关键词：thermoelectrics ; magnesium ; tin ; power factor ; output power
