学生のWei Zhouさん(博士後期課程3年、物質化学領域前之園研究室)が国際熱電会議:The 38th International Conference on Thermoelectrics and The 4th Asian Conference on Thermoelectrics (ICT/ACT2019)においてポスター賞を受賞しました。

 International Conference on Thermoelectrics (ICT)は熱電変換技術に関して最も主要な国際会議です。米国、欧州、アジアという順に毎年1回開催され、今年は第38回目の会議となります。また、アジアでの開催の年にあたり、第4回アジア熱電会議 (4th Asian Conference on Thermoelectrics(ACT)) を兼ねて、6月30日~7月4日の日程で韓国・慶州において開催されました(参加者数643名)。


Structure-property relations in thermoelectric nanobulk materials fabricated from Cu2SnS3 nanoparticles

As one of the promising waste heat harvesting technologies, thermoelectric (TE) materials and devices have attracted considerable interests in recent decades because they offer a promising route to convert waste heat into electrical power. The performance of a thermoelectric material is quantified by the dimensionless figure of merit ZT =σS2T/κ, where σ, S, κ and T are the electrical conductivity, Seebeck coefficient, thermal conductivity and absolute temperature, respectively.
Cu2SnS3 (CTS) system consists of green and abundant elements and exhibits modest TE properties at relatively low temperature range (< 200 degree C). However, the ZT value of CTS is still too low for practical applications. The low ZT (< 0.1) value of bulk CTS encourage researchers to devote to improve the thermoelectric properties of CTS based materials. The challenges associated with increasing the overall ZT value can be observed in the figure of merit equation where electrical conductivity must be increased while thermal conductivity is suppressed. By introducing the effect of nano-structuring, thermal conductivity can be dramatically reduced through enhanced phonon scattering at grain boundaries because of the longer mean free path of phonons than that of mean grain size. In our strategy, we will use nanoparticles (NPs) as building blocks within a pelletized material to control the nanoscale structure while also maintaining the particle attributes. On the other hand, nanoscale and/or mesoscale structures can be controlled by changing sintering conditions and the size and shape of nanoparticles.
The impacts of grain size on thermoelectric properties of this material have not been studied. To investigate the grain size dependence, in this study, CTS nanoparticles with different sizes were chemically synthesized as building block. The mean crystalline size of nanoparticles were changed from 10 to 40 nm without changes of crystal structure. Thereafter, the resulting NPs were further pelletized into a nanobulk material by a pulse electric current sintering method. In this talk, TE properties such as σ, S and κ as well as overall ZT value of the pelletized material will be discussed in terms of composition and structure.

It is my honor to receive the ICT2019 Poster Award at the 38th International Conference on Thermoelectrics (ICT) and the 4th Asian Conference on Thermoelectrics (ACT) 2019. A thanks to the judges, it makes me very happy. I would like to thank my supervisor Prof. Shinya Maenosono for his carful guidance. My thanks will also go to Ms. Pratibha Dwivedi, Mr. Koichi Higashimine, Assist. Prof. Masanobu Miyata, Dr. Michiro Ohta, Mr. Takeo Akatsuka, Mr. Hiroshi Takida, Prof. Mikio Koyano and Ms. Naoko Fujimoto for all the help they gave me during this research work. It is really good memory for me and it will last forever.