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 Mg₃Sb₂-based thermoelectric materials is vitally important to the construction of efficient all-Mg₃Sb₂-based thermoelectric devices. Herein, by utilizing (Mg_3.2Sb₂)_0.5(YbZn₂Sb₂)_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 YbZn₂Sb₂ with Mg and Sb powders, followed by spark plasma sintering, leads to the formation of (Mg_3.2Sb₂)_0.5(YbZn₂Sb₂)_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_3.2Sb₂)_0.5(YbZn₂Sb₂)_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_3.18Ag_0.02Sb₂)_0.5(YbZn₂Sb₂)_0.5 sample exhibits a dimensionless figure of merit (<i>zT</i>) of 1.17 at 773 K and an average <i>zT</i> of 0.69 over 300-773 K, which are among the highest values reported for p-type Mg₃Sb₂-based materials. This study demonstrates the importance of optimizing fabrication processes and compositional tuning in achieving high and stable thermoelectric properties in p-type Mg₃Sb₂-based materials.