Tuning the phonon dynamics via Sn-resonant impurities assists strong anharmonicity in <i>p</i> -type Zintl Mg3Sb2

Mg3Sb2-based Zintl compounds are promising p-type thermoelectric (TE) materials with a hexagonal crystal structure and are considered promising candidates due to their abundance in nature, low cost, and low toxicity. Here, the Sn-substituted p-type Mg3−xZnxSb2-based solid solution was synthesized via spark plasma sintering, and its transport properties were investigated through experimental and theoretical aspects. Sn at Sb sites in Mg1.8Zn1.2Sb2 softens the chemical bonding, and Sn-Sb 5p orbital overlapping introduces resonant states, resulting in an enhanced density of states. The improved carrier concentration of 1.47 × 1019 cm−3 and electrical conductivity of 324 S/cm, with the Seebeck coefficient of 133 μV/K, yielded a maximum power factor of 579.8 μW/mK2 at 753 K. Additionally, Sn doping induced lattice disorders, and point defects led to reduced the sound velocity of 2225 m/s, resulting in a low lattice thermal conductivity of 0.72 W/mK at 753 K. The synergistic effect of an enhanced power factor and suppressed thermal conductivity resulted in a maximum zT of 0.43 at 753 K for Mg1.8Zn1.2Sb1.94Sn0.06. This work underscored the critical role of resonant states and lattice disorders in boosting the TE performance of p-type Mg3−xZnxSb2.