Investigation of the Thermoelectric Performance of PbTe-Ag2Se Derived Pseudo-solid Solutions, Nanostructures and Nano-composites

技术概述：本项目研究PbTe-Ag2-äSe合金的结构形成以及电和热输运性能。PbTe-Ag2-äSe固溶体表现出非常有趣的结构行为，低电阻率和非常低的热导率。因此，该系统有可能为发电应用带来一种新的最先进的热电材料。除了该系统表现出的良好的传输特性外，所得到的合金还具有稳定性和机械稳定性，从而允许过度操控以优化热电性能。观察到PbTe-Ag2-äSe(摩尔比为1：1)的致密固溶体形成了以单相为主的以氯化钠结构结晶的合金。在存在如此高水平的结构无序的情况下，以立方为主的单相合金的稳定性是显著的。PbTe似乎决定了熔体结构的形成，而不是Ag2Se-Ag2Se在低温下稳定在正交结构中，在高温下稳定在立方结构中。PbTe-Ag2-äSe合金是简并半导体，其电输运与Ag浓度有关。初步测量了几个ä=0.1的样品的p型行为和高温(~400oC)总导热系数T 0.6W/m-K。本工作将利用X射线衍射仪和显微技术研究这些合金的结构形成，并研究结构操纵，即进一步合金化、纳米结构和纳米复合材料对热电性能的影响。这项研究将为研究生和本科生提供材料合成和表征方面的优秀培训。非技术综述：该方案将利用固溶体、纳米结构和带隙工程来获得用于发电应用的高效热电合金。开发用于发电的热电材料是我们实现能源独立和安全的科学努力的重要组成部分。热电材料将废热转化为电能，这意味着任何热源，无论是人造的(汽车)还是天然的(温泉)，都可以用来生产电能。热电偶两端的温度梯度的存在会产生电压。热电材料还提供了无需移动部件的机械优势，消除了润滑和频繁维护的需要。本工作将对PbTe-Ag2-äSe合金的结构形成和高温热电性能进行研究。这些合金已被证明具有非常低的导热系数和良好的导电性。为了获得高效的热电材料，两者都是必需的。此外，高温热电性能将通过这些合金的化学和机械加工来优化。这项研究将为研究生和本科生提供材料合成和表征方面的优秀培训。一名研究生和两名本科生将参与这一项目，并将参与这项调查的所有方面。国际和平协会积极鼓励妇女和少数群体参与他的研究。

TECHNICAL SUMMARY:This project investigates structure formation and electrical and thermal transport properties of PbTe-Ag2-äSe alloys. Solid-solutions of PbTe-Ag2-äSe display extremely interesting structural behavior, low electrical resistivity and very low thermal conductivity. Hence, this system has the potential to give rise to a new state-of ?the-art thermoelectric material for power generation applications. In addition to the favorable transport properties exhibited by the system, the resulting alloys are stable and mechanically robust thus allowing excessive manipulation for optimization of the thermoelectric performance. It has been observed that dense solid-solutions of PbTe-Ag2-äSe (1:1 molar ratio) result in a predominantly single phase alloy which crystallizes in the NaCl structure. Stabilization of a predominantly cubic single phase alloy in the presence of such a high level of structural disorder is remarkable. PbTe appears to dictate structure formation from the melt and not Ag2Se - which stabilizes in an orthorhombic structure at low temperatures and cubic at high temperatures. The PbTe-Ag2-äSe alloys are degenerate semiconductors whose electrical transport correlates with Ag concentration. Preliminary measurements on several samples with ä = 0.1 showed p-type behavior and a high-temperature (~ 400 oC) total thermal-conductivity value êT 0.6 W/m-K. This work will investigate the structure formation of these alloys using x-ray diffraction and microscopy, and study the effects of structure manipulation, i.e. further alloying, nano-structuring and nano-composites, on the thermoelectric properties. This research will provide excellent training for graduate and undergraduate students in material synthesis and characterization. NON-TECHNICAL SUMMARY:This proposal will utilize solid-solutions, nano-structuring and band-gap engineering in order to obtain a high efficiency thermoelectric alloy for power generation applications. Development of thermoelectric materials for power generation is an essential component in our scientific effort to achieve energy independence and security. Thermoelectric materials convert wasted heat to electricity, which implies that any heat source, either man-made (automotives) or natural (hot springs) can be utilized for production of electrical energy. The presence of a temperature gradient across the thermoelectric will give rise to a voltage. Thermoelectric materials also offer the mechanical advantage of absence of moving parts, which eliminates the need for lubrication and frequent maintenance. This work will research the structure formation and high temperature thermoelectric performance of PbTe-Ag2-äSe alloys. These alloys have been shown to have very low thermal conductivity and good electrical conductivity. Both are needed in order to obtain an efficient thermoelectric material. Additionally, the high temperature thermoelectric performance will be optimized through the chemical and mechanical processing of these alloys. This research will provide excellent training for graduate and undergraduate students in material synthesis and characterization. One graduate student and two undergraduate students will be working on this project and will be involved in all aspects of this investigation. The PI actively encourages the participation of women and minorities in his research.