Insight on the interplay between synthesis conditions and thermoelectric properties of α-MgAgSb

Kurzfassung

α-MgAgSb is a very promising thermoelectric material with excellent thermoelectric properties between room temperature and 300 °C, a range where few other thermoelectric materials show good performance. Previous reports rely on a two-step ball-milling process and/or time-consuming annealing. Aiming for a faster and scalable fabrication route, herein, we investigated other potential synthesis routes and their impact on the thermoelectric properties of α-MgAgSb. We started from a gas-atomized MgAg precursor and employed ball-milling only in the final mixing step. Direct comparison of high energy ball-milling and planetary ball-milling revealed that high energy ball milling already induced formation of MgAgSb, while planetary ball milling did not. This had a strong impact on the microstructure and secondary phase fraction, resulting in superior performance of the high energy ball milling route with an attractive average thermoelectric figure of merit of zT avg = 0.9. We also show that the formation of undesired secondary phases cannot be avoided by a modification of the sintering temperature after planetary ball milling, and discuss the influence of commonly observed secondary phases on the carrier mobility and on the thermoelectric properties of α-MgAgSb.