Solid State Chemistry: from Thermoelectric to Nonlinear Optical Materials

固态化学：从热电材料到非线性光学材料

• 批准号: RGPIN-2020-04145
• 负责人: Kleinke, Holger
• 金额: $ 4.66万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=716171
• 关键词: Solid; State; Chemistry; Thermoelectric; Nonlinear

Thermoelectric Energy Conversion My NSERC-funded research is focused on the thermoelectric energy conversion. This sustainable energy creation method is becoming increasingly important, as our natural resources continue to decline and mankind's need for electricity increases. Thermoelectric (TE) materials can create electricity via the Seebeck effect from a temperature gradient, and thus from the abundant waste heat, or in turn create a temperature gradient from electricity via the Peltier effect. Most notably, this method of energy generation has been in continuous use in spacecrafts since the early 1960s. Since the better of two decades, TEs have been at the forefront of research into utilizing the waste heat in automotives to reduce the load on the alternator and thereby enhance fuel economy, and for waste heat utilization in stationary applications such as photovoltaics and wood-stoves as well. More widespread applications of the TE effect are still hindered by the comparatively low energy conversion efficiency despite recent success with a number of new materials and strategies. The TE efficiency of a material is evaluated by the dimensionless figure-of-merit, zT, which depends on the Seebeck coefficient, the electrical conductivity, and the thermal conductivity (as well as the temperature). To obtain high efficiency, the materials must exhibit high Seebeck coefficient (high thermopower), high electrical conductivity but low thermal conductivity. Unfortunately all these physical properties depend on the charge carrier concentration, and can therefore not be independently optimized. We will focus on four promising materials classes, with each having different challenges to overcome. Nonlinear Optics A second, new research area is in nonlinear optical (NLO) materials, after our search for new TEs resulted in discovering potential NLO materials. The demand for intense light at various frequencies exceeds what current light sources on the market can deliver. This may be solved by using NLO materials that can modulate the frequencies of light via up-conversion or down-conversion. A classical example is frequency doubling (halving the wavelength) of a Nd:YAG laser from 1064 nm to 532 nm through an NLO material via the second harmonic generation (SHG). Currently NLO materials are being used in communication systems, remote sensing, tissue imaging, environmental monitoring, and minimally invasive surgeries. The optimization of IR NLO materials is complex, for one needs - in addition to a large second-order harmonic generation (SGH) response - also a high laser damage threshold (LDT), a wide IR transmission range, a wide band gap, and phase matching behavior. Specifically, a larger band gap generally results in a higher LDT but smaller SHG. On top of that, a necessary criterion for the existence of NLO behavior is a noncentrosymmetric space group. Here we will explore various main group chalcogenides with promising structural features.

热电能量转换 我的NSERC资助研究集中在热电能量转化上。随着我们的自然资源不断下降，人类对电力的需求增加，这种可持续的能源创造方法变得越来越重要。热电（TE）材料可以通过温度梯度的Seebeck效应创造电力，从而从大量的废热中产生电力，或者又通过Peltier效应从电力产生温度梯度。最值得注意的是，自1960年代初以来，这种能源产生方法一直在航天器中连续使用。由于二十年来更好，因此TE一直处于研究的最前沿，用于利用汽车中的废热来减少交流发电机的负载，从而增强燃油经济性，以及用于固定应用中的废热利用，例如光伏和木材库存也是如此。尽管最近有许多新的材料和策略，尽管最近成功的能源转换效率相对较低，但TE效应的广泛应用仍受到相对较低的能量转换效率的阻碍。 材料的TE效率通过无量纲的ZT进行评估，该ZT取决于Seebeck系数，电导率和导热率（以及温度）。为了获得高效率，材料必须表现出高的Seebeck系数（高热电器），高电导率，但导热率较低。不幸的是，所有这些物理特性都取决于电荷载体浓度，因此不能独立优化。我们将专注于四个有前途的材料课，每种都有不同的挑战以克服。 非线性光学 在我们寻找新的TES导致发现潜在的NLO材料之后，第二个新的研究领域是非线性光学（NLO）材料。在各种频率下对强光的需求超过了市场上当前的光源所能提供的。可以通过使用NLO材料来解决这一问题，该材料可以通过上转换或下转换来调节光的频率。一个经典的示例是通过第二次谐波生成（SHG）通过NLO材料（SHG）通过NLO材料将nd：yag激光器的波长加倍（将波长减半）。目前，NLO材料已用于通信系统，遥感，组织成像，环境监测和微创手术。对于一个需求而言，IR NLO材料的优化是复杂的 - 除了大型二阶谐波生成（SGH）响应 - 还具有高激光损伤阈值（LDT），广泛的IR传输范围，宽带隙和相位匹配行为。具体而言，较大的带隙通常会导致更高的LDT但SHG较小。最重要的是，NLO行为存在的必要标准是一个非中心空间群。在这里，我们将探索具有有希望的结构特征的各种主要组葡萄构化。