Effects of sintering on the microstructure and electrical properties of ZnO-based thermoelectric materials

Publication date: 15 October 2017
Source:Materials & Design, Volume 132
Author(s): Tian Tian, Lihong Cheng, Juanjuan Xing, Liaoying Zheng, Zhenyong Man, Dongli Hu, Slavko Bernik, Jiangtao Zeng, Jia Yang, Yi Liu, Guorong Li
Both the spark plasma sintering (SPS) method and reducing atmosphere sintering (N2+CO) method could greatly improve the electrical performance of ZnO-based thermoelectric materials. However, there is no comparison of these two methods which is essential for further improvements to the thermoelectric performance. In this article, a systematic comparison of the microstructures and electrical properties of the ZnO-based thermoelectric materials prepared by the SPS method, the reducing atmosphere sintering (N2+CO) method, and the conventional sintering method was presented. The ZnO-based thermoelectric materials prepared by the reducing atmosphere sintering (N2+CO) method showed the highest power factor with a moderate carrier concentration and a high Hall mobility, while the sample prepared by the SPS method exhibited the highest electrical conductivity of 2.3×10⁵S·m⁻¹ with a lower power factor. The ultra-high electrical conductivity of the SPS processed sample was mainly due to the increased solubility of Ti, which led to a higher carrier concentration. Moreover, the grain-boundary structure, which is important for the electrical performance, was also systematically analyzed by EBSD and CL. It can be concluded that the reducing atmosphere sintering (N2+CO) method is more suitable for thermoelectric applications, while the SPS method is an effective way to produce highly conductive ZnO ceramics.

Graphical abstract

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