Rational Design of Thermoelectric Materials and Material Processing Approaches Based on Microwave Processing of Silicides

热电材料是当材料的两侧暴露于不同温度时能够产生电流的材料，反之亦然（即，向热电材料提供电压和电流可以改变其表面的温度）。热电材料是一种很有前途的技术，应用范围从发电到加热和冷却。今天的大多数电力都是从燃料燃烧产生热量的过程中产生的，这些热量将水转化为蒸汽，然后用于驱动发电机，而低温蒸汽则作为废物排出。 这些过程相对低效，仅将约30%至40%的燃料能量转化为有用的电力。 热电材料可用于将这些浪费的热能转化为有用的电能。 该团队将设计和构建高效率的热电材料和设备的复合材料构成的组合非晶（即，非晶体、分子无序）和晶体材料，可以最大限度地提高材料的导电性，同时最大限度地降低材料的导热性，这是有效热电的理想组合。该项目将有广泛的教育影响，通过纳米技术相关的大学课程的发展，并通过在研究中的代表性不足的学生的直接参与。工作的主要重点将是使用复合硅化物（即，联合收割机的材料）以产生高效的热电。更高效的热电材料的目标是实现大的热电效应，使得可以从废热源和环境之间的相对小的温差产生大量的电力。 该项目是一个计算指导的材料设计工作，包括理论和实验方面的非晶材料。该计划解决了在扩展和本地化的状态，沿着与声子输运性质在无序的多组分非晶结构中的载流子的多模输运。预计在这项工作中开发的硅化物合金的非晶-晶体复合材料的基础上的新材料结构应导致显着的非线性增强的热电功率因数，沿着材料的热导率的降低。这一研究概念是一种纳米级效应，只有当载流子的能量分布函数不松弛到微晶中的大块材料的能量分布函数时才会发生这种效应。在大多数热电材料中，这种状态需要低于10 nm的微晶尺寸，这通常难以用现有的材料加工方法达到。本计画将发展一种新的材料合成方法，以微波腔场分解为基础，可产生非平衡硅化物材料。将首次研究氢化对热电性能的影响，并展示材料生长技术的可扩展性

Thermoelectric materials are materials that can produce an electric current when two sides of the material are exposed to different temperatures or vice-versa (i.e., supplying an electric voltage and current to a thermoelectric material can change the temperature of its surfaces). Thermoelectric materials are a promising technology for a range of application from electric power generation to heating and cooling. Most electric power today is produced from processes where fuel is burned to produce heat that turns water into steam that is then used to turn electric power generators, and low temperature steam is exhausted as waste. Such processes are relatively inefficient, converting only about 30 to 40 percent of the fuel's energy into useful electric power. Thermoelectric materials could be used to convert this wasted thermal energy into useful electric power. The team will design and construct high efficiency thermoelectric materials and devices from composite materials constructed from combinations of amorphous (i.e., non-crystalline, molecularly disordered) and crystalline materials that can maximize the material's electrical conductivity while minimizing the material's thermal conductivity, an ideal combination for effective thermoelectricity. The project will have broad educational impacts through both development of nanotechnology related university-level coursework and through the direct involvement of underrepresented students in the research.The primary focus of the work will be on the use of composite silicide (i.e., materials that combine silicon with other elements such as metals) to create highly efficient thermoelectrics. The target of more efficient thermoelectric materials is to achieve a large thermoelectric effect so that large amounts of electric power can be generated from relatively small temperature differences between waste heat sources and the environment. This project is a computationally guided material design effort which encompasses both theoretical and experimental aspects of amorphous based materials. The program addresses the multi-mode transport of charge carriers in extended and localized states, along with phonon transport properties in disordered multi-component amorphous structures. It is expected that new material structures based on amorphous-crystalline composites of silicide alloys developed in this work should result in significant nonlinear enhancement of the thermoelectric power factor, along with the reduction of the thermal conductivity of the materials. This research concept is a nanoscale effect that happens only if the energy distribution function of the carriers does not relax to that of the bulk material in the crystallites. This state requires crystallite sizes of sub-10 nm in most thermoelectric materials, which is often difficult to reach with the existing material processing methods. This project will develop a new material synthesis method based on field decrystallization in a microwave cavity that can produce non-equilibrium silicide materials. The effect of hydrogenation on thermoelectric properties will be investigated for the first time, and the scalability of the material growth technique will be demonstrated