Development of thermoelectrically active and thermally sprayed ceramics

经济型热电发电机的制造需要有效的生产技术。热喷涂有可能成为一种具有成本效益的替代方法，但必须解决重大的机械和技术挑战。热喷涂是由具有热电活性的p、n半导体以及电绝缘和导电材料组成的多层体系，可通过热喷涂实现。喷涂材料的性能不仅取决于喷涂工艺，还取决于原料的质量。虽然电绝缘或导电材料在热喷涂中是众所周知的，但热电活性材料却很少被研究。开发高性价比的热塑性弹性体材料是热塑性弹性体生产的迫切需要。特别是对于热喷涂加工，除了通常关于电导率和热导率以及塞贝克系数的要求外，热电材料还应该是可喷涂的，具有低毒性，并可大量获得。氧化物材料具有最高的潜力来满足这些要求。然而，要了解这些材料在喷涂过程中的具体材料行为并提高它们的ZT值，还需要付出大量的努力。因此，该项目的重点在于开发环境友好、经济可行的热电材料，这种材料可以通过热喷涂进行加工。掺杂氧化锌由于其良好的喷雾性能和良好的热电性能，是最合适的氧化物材料之一。该项目的主要目标是生产机械稳定的热电活性涂层，厚度约500微米，在600°C以上的温度下ZT至少为0.3。为此，必须开发和制造一种以粉末和悬浮液形式的量身定制的喷涂喂料，并研究不同热喷涂方法的工艺参数与涂层性能(热电、结构、物理)之间的关系。

The manufacture of economical thermoelectric generators (TEG) requires effective production technologies. Thermal spraying has the potential to be a cost-effective alternative for the production of TEGs, but major mechanical and technological challenges have to be addressed. TEG's can be realized by thermal spraying as a multi-layer system consisting of the thermoelectrically active p and n semiconductors, as well as electrically insulating and electrically conductive materials. The properties of the sprayed materials depend not only on the spray process but also on the quality of the feedstock material. While electrically insulating or conductive materials are well known in thermal spraying, thermoelectrically active materials have rarely been studied. The development of cost-effective TE materials is an urgent need for the production of TEGs. In particular for the processing by thermal spraying, in addition to the usual requirements concerning electrical and thermal conductivity and the Seebeck coefficient, the thermoelectric material should also be sprayable, have a low toxicity and be available in high amounts. Oxide materials have the highest potential to fulfill there requirements. However significant effort is required in order to understand the specific material behavior of these materials during the spray process and to improve their ZT values. Therefore, the focus of this project lies in the development of environmentally friendly and economically viable thermoelectric materials, which can be processed by thermal spraying. Doped zinc oxide is, due to its sprayability and promising thermoelectric properties, one of the most suitable oxide materials. The main goal of the project is the production of thermoelectrically active coatings which are mechanically stable, ca. 500 µm thick, and present a ZT of at least 0.3 at temperatures above 600 ° C. For this purpose, a tailored spray feedstock, in the form of powders and suspensions, has to be developed and manufactured, and the relationship between the process parameters of the different thermal spray methods and the coatings properties (Thermoelectric, structural, physical) has to be studied.