First-Principles Thermoelectric Study of SrMgSi and CaMgGe Zintl-Phase Compounds

Zintl-phase semiconductor materials with low intrinsiclatticethermal conductivity have been the target of study for thermoelectric(TE) applications. Herein, we report Zintl-phase TiNiSi-type SrMgSiand CaMgGe with calculated low intrinsic lattice thermal conductivity(& kappa;(L)) values of 2.52 and 1.90 W/m & BULL;K at room temperature,respectively. The low & kappa;(L) is mainly due to the stronglattice anharmonicity, which originates from the weak bonding of cationsin the anionic network, and strong optical-acoustic phonon coupling.Additionally, the high band degeneracy results in good electricalproperties, and excellent ZT values of & SIM;2.83(n-type, 500 K) and 3.09 (n-type, 500 K) are predicted for SrMgSiand CaMgGe, respectively. The theoretical study provides a valuabledirection for exploring Zintl-phase materials for efficient TE powerconversion.

Automated summary

In this study, Zintl-phase TiNiSi-type SrMgSi and CaMgGe with low intrinsic lattice thermal conductivity were investigated for thermoelectric applications. The low thermal conductivity is attributed to the strong lattice anharmonicity and optical-acoustic phonon coupling, while the high band degeneracy leads to good electrical properties. The predicted ZT values for SrMgSi and CaMgGe were 2.83 and 3.09, respectively.