The thermoelectric performance of the BaCaSn compound is systematically investigated through first-principles calculations and Boltzmann transport theory in the current work. The BaCaSn compound features a ${{\left[\mathrm{Ca}\text{−}\mathrm{Sn}\right]}^2}^{-}$ anionic framework interlaced with $\mathrm{B}{\mathrm{a}}^{2+}$ cation. The intricate bond lengths and distorted bond angles within the anionic framework facilitate efficient carrier transport while simultaneously enhancing the anharmonic lattice dynamics. Electronic structure analysis reveals that the BaCaSn compound is an indirect semiconductor with a bandgap of 0.71 eV. The sharp conduction band distribution improves electron mobility, while the multivalley nature of the valence band increases the hole effective mass, significantly enhancing the Seebeck coefficient. In terms of thermal transport, the weak interaction between $\mathrm{B}{\mathrm{a}}^{2+}$ cation and the ${{\left[\mathrm{Ca}\text{−}\mathrm{Sn}\right]}^2}^{-}$ anionic framework leads to pronounced rattling dissipation behavior, which significantly enhances phonon scattering and reduces phonon group velocity, thus exhibiting typical phonon glass behavior. Notably, the $p$-type doping strategy significantly increases the power factor due to the multivalley effect, thereby resulting in an excellent thermoelectric performance. The BaCaSn compound demonstrated figure of merit values of 1.1 and 0.8 under $p$-type and $n$-type doping conditions at 700 K, respectively. This work not only elucidates the fundamental physicochemical mechanisms governing the coupled electron-phonon transport in the BaCaSn compound, but also provides critical theoretical insights for the rational design of advanced thermoelectric materials.

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• Electrocaloric effect
• Thermoelectric effects
• Thermoelectrics
• Boltzmann theory
• First-principles calculations