Morphology and Thermoelectric Properties of Mg_3+δSb₂ Foams Manufactured Using Combustion Synthesis

Abstract

Magnesium antimonide (Mg₃Sb₂) is a promising thermoelectric compound utilized for thermoelectric power generation. We have found out that the Mg₃Sb₂ compound can be made from Mg and Sb powder mixture via the combustion synthesizing reaction. In this study, we manufactured the compounds from the compacted bodies with different Mg fractions between 60.0 and 75.0 at% in an argon gas flow at 650°C for 1 hour via the combustion synthesis process. Morphology, porosity, phases and thermoelectric properties (electrical resistivity and Seebeck coefficient at room temperature to 500°C) were investigated for the manufactured samples. All samples manufactured with different Mg fractions mainly consisted of Mg₃Sb₂ and became foamed bodies with a porosity between 50 and 70%. The thermoelectric properties changed with the Mg fraction. The maximum power factor of 42.1 µW/mK² at 488°C was obtained in the foamed body with the Mg fraction of 64 at%. The dimensionless figure of merit (ZT) of the sample was also estimated using the thermal conductivity, which was calculated considering its large porosity. The maximum dimensionless figure of merit (ZT_max) would be 0.13 at 488°C.

 

This Paper was Originally Published in Japanese in J. Jpn. Soc. Powder Powder Metallurgy 68 (2021) 399–404.

Figure (a) curve profile of differential scanning calorimeter during heating Mg+Sb powder compact (Mg fraction 60 at%) in N₂ gas flow, and (b) cross-section image of Mg₃Sb₂ formed body (Mg fraction 60 at%).