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The recently discovered Zintl compound Yb10MnSb9 is a thermoelectric material very close in compositional space to high performing thermoelectric materials such as Yb14Mn1Sb11 and Yb21Mn4Sb18. Here we measure and report...

Yb10MgSb9 is a new Zintl compound (with a composition closer to Yb10.5MgSb9) and a promising thermoelectric material first reported in this work. Undoped Yb10MgSb9 has an ultralow thermal conductivity due to crystallographic complexity and exhibits a relatively high peak p‐type Seebeck coefficient and high electrical resistivity. This is consistent with Zintl counting and density functional theory (DFT) calculations that the composition Yb10.5MgSb9 should be a semiconductor. Na is found experimentally to be an effective p‐type dopant potentially due to the replacement of Na+ for Yb2+, allowing for a significant decrease in electrical resistivity. With doping, a dramatic improvement of electrical conductivity is observed and the glass‐like thermal conductivity remains low, allowing for a significant enhancement of the thermoelectric figure of merit, zT. Doping increases the zT from 0.23 in undoped Yb10MgSb9 to 1.06 in 7 at% Na‐doped Yb10MgSb9 at 873K. This high thermoelectric performance found through Na‐doping places this material amongst the leading p‐type Zintl thermoelectrics, making it a promising candidate for future studies and high‐temperature thermoelectric applications.

Seebeck coefficient of VFe2Al over a wide range of doping levels can be explained only with a small band-gap (Eg) range of 0.02–0.04 eV. This Eg value is also consistent with high-temperature resistivity data of nominally stoichiometric VFe2Al.