Insight on the Interplay between Synthesis Conditions and Thermoelectric Properties of α-MgAgSb

Abstract

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 z T 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.

Impact of impurities and time on thermoelectric performance of MgAgSb

“…2 lists the average values of carrier concentration and mobility of MgAgSb samples prepared at the various sintering temperatures, conducted at two durations. The mobility of these sam-ples is better than the values obtained by [7] using both BM and HEBM techniques to synthesize MgAgSb. Mobility of the material is the ability of an electron to move in a material in the presence of an applied electric field electrical conductivity, i.e., greater is the carrier concentration and mobility of a sample higher is the electrical conductivity and vice versa, which is given by equation.…”

“…Camut et al [7] prepared MgAgSb (ZT~1.1) through both planetary ball milling and high energy ball milling followed by hot pressing through spark plasma sintering (SPS). Various impurities (Mg3Sb2, Ag3Sb, Sb) were observed in synthesized samples, and a clear impact on the decrease in the ZT value of the prepared product was presented.…”

Establishing synthesis–composition–property relationships for enhanced and reproducible thermoelectric properties of MgAgSb

“…This is in line with earlier results and speculations. 16,25,26 The effective composition was determined for each sample in order to observe its inuence on the thermoelectric properties.…”

“…However, even though a synthesis route has been established 20 and repeatedly employed, the experimental results show that the thermoelectric properties are not easily reproducible. Indeed, several recent works on MgAgSb based devices report lower TE properties, zT avg = 0.9, 22 zT avg = 0.9, 25 zT avg = 0.77, 26 compared to the original publication of Liu et al reporting zT avg = 1.1 (ref. 16) even though all followed the same synthesis route.…”

Numerical and Experimental Study on the Performance of Thermoelectric Radiant Panel for Space Heating

“…Among the many applications of TEMs, the thermoelectric radiant panel (TERP) has much interest owing to its good constructability, compact size, and potential as a parallel cooling and heating device under stable thermal loads [21]. It has a limitation by the low performance value, which is evaluated as the figure of merit of thermoelectric materials (ZT) [22,23], however the recent advances in thermoelectric material make it possible to improve the ZT value [24][25][26][27]. Additionally, TERP does not require an additional heat exchanger for cooling or heating the liquid or air and it can be directly attached on the radiant cooling/heating surface.…”