The 83rd JSAP Autumn Meeting 2022 Highlighted Presentations
October 24, 2022

Development of High Efficiency P-type GeTe / N-type Mg3Sb2! Thermoelectric Module

Contributing to the Realization of Carbon Neutrality via theUtilization of Exhaust Heat
Highly Efficient Thermoelectric Module Achieves Worldclass Power Generation Density
Panasonic Holdings (1), AIST (2)Fuyuki Ando (1), Hiromasa Tamaki (1), Yoko Matsumura (2), Tomoyuki Urata (2), Takeshi Kawabe (1), Ryosuke Yamamura (1), YurikoKaneko (1), Ryoji Funabashi (2), Tsutomu Kanno (1)summary• A coin-sized thermoelectric module that enables one of the world's highest power
generation densities of up to 8.5 W (1.62 W/cm2) is developed.
• Applied Materials Informatics: A computational science-based search for material
exploration of thermoelectric conversion materials to be utilized in thermoelectricmodules. The current cost of the search has been reduced to 10 % of the original cost.
• This research is on a technology that recycles a part of waste heat, which corresponds to60 % of the primary energy, into electricity; thus, this technology has the potential tocontribute significantly to carbon neutrality.

A research group led by Fuyuki Ando, Hiromasa Tamaki, Takeshi Kawabe, Ryosuke Yamamura, YurikoKaneko, and Tsutomu Kanno of the Technology Division of Panasonic Holdings Corporation; and Yoko
Matsumura, Tomoyuki Urata, and Ryoji Funabashi of the Nanomaterials Research Institute, AIST, developed
a novel thermoelectric module that generates electricity from waste heat. The group succeeded indeveloping N-type Mg3Sb2 (magnesium antimony) and P-type GeTe (germanium telluride) materials asthermoelectric conversion materials with high performance, thereby achieving a world-class power
generation density of up to 8.5 W (1.62 W/cm2) in coin size (21mm×25mm) at a temperature difference of560 !. This study is expected to be a technological development that will contribute to the reduction of CO2
emissions and achieve carbon neutrality.
detailSixty percentage of waste heat that is continually discarded is a future resource
Japan aims to be carbon-neutral by 2050, with the goal of reducing greenhouse gases emission to virtuallyzero by subtracting the amount absorbed by nature and other processes from the amount emitted. To
achieve this goal, the industrial sector has taken measures to reduce the emissions of CO2 and othergreenhouse gases. A research group led by Panasonic Holdings et al. developed a novel thermoelectricmodule that generates electricity from waste heat, essentially aiming to reduce greenhouse gas emissions inthe society.
According to a survey by the Agency for Natural Resources and Energy, approximately 60 % of the primaryenergy mainly obtained from fossil fuels and other sources is discarded as unused waste heat. Herein, theresearch group intend to reduce the overall energy supply and CO2 emissions by utilizing unused waste heat(discarded from primary energy) via the thermoelectric module they have developed (Figure 1). The researchgroup has been exploring thermoelectric conversion materials with high performance in the medium–hightemperature range of 300–500 °C and demonstrated a world-class power generation density of up to 8.5 W(1.62 W/cm2) in a coin-sized thermoelectric module with a temperature difference of 560 °C (Figure 2).

“Unlike typical thermal power generation, thermoelectric modules enable clean power generation that do notemit CO2 gas. One of the advantages of thermoelectric modules is to be flexibly applied to various heatsources of different scales. Furthermore, the modules contain no moving parts; therefore, they are almost
maintenance-free and have a long service life. We believe that by adopting this thermoelectric module, wecan effectively utilize waste heat that have been difficult to recover in the past, thereby contributing to thereduction of CO2 emissions,” says Ando.
Computational Science Accelerates the Search for Counterpart P-type MaterialThermoelectric modules utilize the Seebeck effect, which directly converts the temperature differences
between objects into voltage. Thermoelectric modules require both N-type and P-type thermoelectric
conversion materials (Figure 3); we have already developed the N-type Mg3Sb2 (magnesium antimony)based material as a promising material, which achieves the world-class thermoelectric performance in thetemperature range of 300–500 °C. Another issue is the exploration of an appropriate p-type thermoelectric
conversion material. In this regard, we introduced materials informatics, a material search method based oncomputational science.

“In the flamework for the development of P-type GeTe, a proper combination of elements that could replace
the germanium site (Ge) and improve the thermoelectric performance had to be identified; however, over20
elements can replace Ge sites. Thus, determining multiple candidate combinations, such as the one wediscovered, would require more than 1, 000 trial runs. This is a tremendous task if it were to be done
manually; however, we were able to achieve this result by improving R&D efficiency via materials
informatics," says Ando.
Having discovered GeInSbTiTe as a P-type material, we successfully developed a thermoelectric modulethat enables a world-class power generation density of up to 1.62 W/cm2. Ando feels the future of material
exploration and device development.
“Note that a conventional, haphazard search for materials would have caused the development to take 10times longer. To date, several developments had to be abandoned because of the increased costs
associated with the sheer volume of such material searches. However, I am convinced that we were able toprove that the possibilities of materials exploration can be expanded by utilizing materials informatics,” says
Ando.

World's Best-in-Class Thermoelectric Module Toward Half Payback Period
Thermoelectric modules have a potential to wide range of applications, including exhaust heat from factories
at the industrial level, energy conservation in the private sector by utilizing exhaust heat from gasoline car
engines, and various types of backup power sources. The advantage of the newly developed module is its
high power-generation density, which minimizes the payback period for capital investment.
“The power generation density is approximately double that of conventional thermoelectric modules;
therefore, the payback period can be cut in half from more than 15 years, which was needed to pay for theinvestment. We feel that lowering the barriers to the introduction of this technology is significant for realizing
a society in which unused waste heat is eliminated,” says Ando.
In future, the company intends to approach the gasoline-powered automobile industry and the steel andceramic industries, which generate enormous amounts of unused waste heat on factory lines.
annotation!Seebeck effect:" A type of thermoelectric effect where two different types of conductors (thermoelectric materials) areconnected to form a circuit. A voltage is generated between the conductors, and current flows in the circuit when atemperature difference is applied to the contact point of each conductor.

figuresFigure 1. Currently, approximately 60 % of primary energy is discarded as unused waste heat. To realize a carbon
neutral society, unused waste heat must be recovered and recycled as usable energy.

Figure 2. Fifteen pairs of P-type GeTe and N-type Mg3Sb2 thermoelectric modules.

Figure 3 Thermoelectric modules have a π-type structure with two types of thermoelectric conversion materials, P-typeand N-type, connected to electrodes.