Suppressed secondary phase generation in thermoelectric higher manganese silicide by fabrication process optimization

Controlling the generation of secondary phases in thermoelectric higher manganese silicides is crucial to enhance their thermoelectric performance for use in automotive thermoelectric generators. However, the effect of different synthesis and sintering procedures on the secondary phase formation and thermoelectric properties has not yet been investigated. In this study, we demonstrate that fabricating Mn₁₁Si₁₉ via arc melting and spark plasma sintering results in a figure of merit (ZT) of 0.43 at 823 K, which is 15% higher than for a sample fabricated by a solid-state reaction and spark plasma sintering. We found that the presence of secondary MnSi phases in the Mn₁₁Si₁₉ samples was significantly reduced when using arc melting instead of solid-state reaction, which suggests that the phase formation behavior could be controlled by optimizing the fabrication process.