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: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=739473
• 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资助的研究集中在热电能量转换。这种可持续的能源创造方法正变得越来越重要，因为我们的自然资源继续下降，人类对电力的需求增加。热电（TE）材料可以通过塞贝克效应从温度梯度中产生电力，从而从丰富的废热中产生电力，或者反过来通过珀耳帖效应从电力中产生温度梯度。最值得注意的是，自20世纪60年代初以来，这种发电方法一直在航天器上使用。近二十年来，TE一直处于研究的前沿，利用汽车中的废热来减少交流发电机的负载，从而提高燃油经济性，并在固定应用中利用废热，如光催化剂和木材炉。TE效应的更广泛应用仍然受到相对较低的能量转换效率的阻碍，尽管最近成功地使用了许多新材料和策略。 材料的TE效率通过无量纲品质因数zT来评估，zT取决于塞贝克系数、电导率和热导率（以及温度）。为了获得高效率，材料必须表现出高塞贝克系数（高热功率）、高导电性但低导热性。不幸的是，所有这些物理性质都取决于载流子浓度，因此不能独立地优化。非线性光学第二个新的研究领域是非线性光学（NLO）材料，在我们寻找新的TE之后，发现了潜在的NLO材料。对各种频率的强光的需求超过了市场上现有光源所能提供的。这可以通过使用可以经由上变频或下变频来调制光的频率的NLO材料来解决。一个经典的例子是Nd：YAG激光器通过NLO材料经由二次谐波产生（SHG）从1064 nm到532 nm的倍频（波长减半）。目前，NLO材料正用于通信系统、遥感、组织成像、环境监测和微创手术。IR NLO材料的优化是复杂的，因为除了大的二阶谐波产生（SGH）响应之外，还需要高激光损伤阈值（LDT）、宽IR透射范围、宽带隙和相位匹配行为。具体地，较大的带隙通常导致较高的LDT但较小的SHG。最重要的是，非线性光学行为存在的一个必要条件是非中心对称空间群。在这里，我们将探讨各种主族硫属化合物与有前途的结构特征。