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B2: Module design

Development of new silicide thermoelectric modules

Ryoji FUNAHASHI1, 4, Yoko MATSUMURA1, Ryosuke O. SUZUKI2, 4, Shigeru KATSUYAMA3, Tomonari TAKEUCHI1, Emmanuel COMBE1, Tristan BARBIER1
1 National Institute of Advanced Industrial Science and Technology, 2 Hokkaido University, 3 Osaka University, 4 CREST Japan Science and Technology Agency

Thermoelectric conversion is attracting attention because it is the strongest candidate to generate electricity from dilute waste heat sources. Waste heat higher than 473 K is high quality energy and the amount of the energy is huge. Some of silicide materials are considered to be promising ones because of their durability against high temperature, no content of toxic elements etc. Recently, a silicide material with good n-type thermoelectric properties and oxidation resistance has been discovered [1]. The composition and crystal structure of the silicide are found out Mn3Si4Al2 and hexagonal CrSi2 structure, respectively. Element substitution of Mn with 3d transition metals is succeeded. Enhancement of Seebeck coefficient is observed in a Cr-substituted sample. The maximum dimensionless thermoelectric figure of merit ZT is 0.3 at 573 K in air for the Mn2.7Cr0.3Si4Al2. The silicide thermoelectric modules consisting of 14 pairs of the legs have been fabricated using MnSi1.75 and non Cr substituted Mn3Si4Al2 devices as p- and n-type legs, respectively. Power generation and durabilty tests of the modules have been carried out. The maximum density of power against the area of the substrate is as high as 3.9 kW/m2. Deterioration of the generated power was observed at temperatures of the hot side higher than 773 K in air. However, no decrease in the generated power was detected for longer than 3 days in vacuum.

1. R. Funahashi, et. al., J. Appl. Phys., 112, 073713 (2012).