Improvement of the Thermoelectric Properties of p-Type Mg₃Sb₂ by Mg-Site Double Substitution

A P-type Mg₃Sb₂-based Zintl phase compound has been considered a promising candidate for thermoelectric applications. Alloying, which introduces a high concentration of point defects, is particularly effective in scattering phonons and reducing lattice thermal conductivity. Herein, alloying in p-type Mg_2.995Na_0.005Sb₂ via the introduction of elements like Yb, Eu, Ca, and Ba was realized, and the room-temperature lattice thermal conductivity has been effectively reduced to ∼1.1 W m^-1 K^-1. To further intensify the phonon scattering, two groups of elements (Eu and Cd, and Yb and Cd) were chosen for heavy alloying at the Mg site, and the lattice thermal conductivity of Mg_1.49Eu_0.5Cd₁Na_0.01Sb₂ was further reduced to ∼0.45 W m^-1 K^-1. Eventually, a peak zT as high as ∼1.0 was achieved at 773 K, and the compound outperforms the previously reported p-type Mg₃Sb₂ compounds.