Reardon Hazel, Blichfeld Anders B, Kasai Hidetaka, Yin Hao, Bøjesen Espen Drath, Iversen Bo B
Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, 8000 Aarhus, Denmark.
Phys Chem Chem Phys. 2017 Jun 21;19(24):15734-15744. doi: 10.1039/c7cp01753g.
Inconsistencies in high temperature thermoelectric property measurements of BaGaGe have prompted our study on the thermal stability of this heavily studied inorganic clathrate. Using X-ray diffraction, thermal analysis, and imaging techniques on both powder and spark plasma sintered pelletized samples, we probe the structure and decomposition characteristics of this important high temperature thermoelectric material. We demonstrate that the decomposition of BaGaGe is extremely dependent on the heating conditions employed and, as a result of the slow decomposition kinetics of the clathrate, reveal that the true stability of this system has been overlooked in the extensive literature available. Loss of Ga and Ge from the clathrate cage is evident in all high temperature experiments under both air and inert environments. This study serves to highlight that the underlying structural chemistry and stability of thermoelectric materials at high temperature needs to be considered in parallel with the thermoelectric properties which constitute the figure of merit. Only then will reliable thermoelectric modules for real applications be realized.
BaGaGe高温热电性能测量结果的不一致促使我们对这种被大量研究的无机笼合物的热稳定性展开研究。通过对粉末样品和火花等离子烧结造粒样品进行X射线衍射、热分析及成像技术，我们探究了这种重要的高温热电材料的结构和分解特性。我们证明，BaGaGe的分解极其依赖所采用的加热条件，并且由于笼合物缓慢的分解动力学，揭示出在现有的大量文献中该体系的真正稳定性被忽视了。在空气和惰性环境下的所有高温实验中，笼合物笼中Ga和Ge的损失都很明显。这项研究旨在强调，在考虑构成品质因数的热电性能的同时，需要并行考虑热电材料在高温下的潜在结构化学和稳定性。只有这样，才能实现适用于实际应用的可靠热电模块。
