Achieving Excellent and Stable Thermoelectric Properties in p-Type (Mg _3.2 Sb ₂ ) _0.5 (YbZn ₂ Sb ₂ ) _0.5 -Based Materials via Optimizing Fabrication Processes

Developing high-performance p-type Mg 3 Sb 2 -based thermoelectric materials is vitally important to the construction of efficient all-Mg 3 Sb 2 -based thermoelectric devices. Herein, by utilizing (Mg 3.2 Sb 2 ) 0.5 (YbZn 2 Sb 2 ) 0.5 as an example, we demonstrate that optimizing fabrication processes is crucial to the achievement of excellent and stable thermoelectric properties. High-energy ball milling of melting–annealing-fabricated YbZn 2 Sb 2 with Mg and Sb powders, followed by spark plasma sintering, leads to the formation of (Mg 3.2 Sb 2 ) 0.5 (YbZn 2 Sb 2 ) 0.5 pellets with dense microstructures and stable thermoelectric properties during repeated testing. Further, the optimized synthesis route facilitates the fabrication of Ag-doped (Mg 3.2 Sb 2 ) 0.5 (YbZn 2 Sb 2 ) 0.5 samples with high relative density and stable thermoelectric properties, in which Ag doping effectively boosts the carrier concentration and power factor. Eventually, the (Mg 3.18 Ag 0.02 Sb 2 ) 0.5 (YbZn 2 Sb 2 ) 0.5 sample exhibits a dimensionless figure of merit ( zT ) of 1.17 at 773 K and an average zT of 0.69 over 300–773 K, which are among the highest values reported for p-type Mg 3 Sb 2 -based materials. This study demonstrates the importance of optimizing fabrication processes and compositional tuning in achieving high and stable thermoelectric properties in p-type Mg 3 Sb 2 -based materials.