Hydride assisted synthesis of the high temperature thermoelectric phase: Yb14MgSb11

Yb14MnSb11 is a p-type high temperature thermoelectric material that has been shown to have a peak zT of 1.3 at 1273 K and stable lifetime testing at that temperature for over 1500 h by NASA. Yb14MgSb11 is a structural analog, but the highest temperature thermoelectric properties have not yet been reported. Yb14MgSb11 has been prepared in an environmentally friendly route employing metal hydrides to provide phase pure samples with excellent control of stoichiometry. We present a comparative study employing either MgH2 or YbH2 as a reactive precursor that also facilitates milling of the elements. High purity compositions are synthesized, and their high temperature thermoelectric properties were measured on dense pellets. Temperature-dependent thermoelectric properties were measured from 300 to 1273 K. Yb14MgSb11 exhibited a peak zT = 1.2 at 1273 K due to an appreciable power factor and low-lattice thermal conductivity. Carrier concentration and hall mobility were also measured from 300 to 1275 K and ranged from 5.3 × 1020 to 1.3 × 1021 cm−3 and from 4.7 to 0.7 cm2 V−1 S−1, respectively.