Thermoelectric properties and low thermal conductivity of Zintl compound Yb 10 MnSb 9

The recently discovered Zintl compound Yb 10 MnSb 9 is a thermoelectric material very close in compositional space to high performing thermoelectric materials such as Yb 14 MnSb 11 and Yb 21 Mn 4 Sb 18 . Here we measure and report electronic and thermal transport data for Yb 10 MnSb 9 up to 825 K. Due to the complicated crystal structure, this material has ultralow thermal conductivity. The ultralow lattice thermal conductivity in conjunction with a higher Seebeck coefficient than in other Yb–Mn–Sb compounds, leads to a moderate zT of about 0.34 at 825 K and is likely to peak at a higher value via material optimization. We approximate a bandgap of about 0.4 eV and expect the zT to be able to reach values as high as 0.33 at 725 K (which is comparable to Yb 14 MnSb 11 at that temperature) using a thermoelectric quality factor analysis. This zT has the potential to reach even higher values by improving the quality factor, B , through grain boundary engineering. Here we provide suggestions for future studies to improve thermoelectric performance. This work is the first report of thermal conductivity, bandgap, and zT for this Yb 10 MnSb 9 compound, and we discuss implications of this material for future thermoelectric study through comparisons to the leading Yb 14 MnSb 11 material.