Effect of Ca Doping on the Thermoelectric Performance of Yb_(14)MnSb_(11)

Complex Zintl phases possess low thermal conductivity and can be easily doped to modify the transport properties. Therefore, these phases have the potential to be good thermoelectric materials by simply controlling carrier concentration. Yb_(14)MnSb_(11) is a Zintl phase that has shown promise as a p-type thermoelectric material for high-temperature power generation. A Sn-flux synthetic route was used to make the new phase, Yb_(13)CaMnSb_(11). The high-temperature thermoelectric properties were measured on polycrystalline hot-pressed pellets and compared with Yb_(14)MnSb_(11). Substitution of the lighter isovalent Ca for Yb should reduce the lattice thermal conductivity by mass disorder scattering, and a noticeable reduction is seen in thermal diffusivity measurements at high temperature. There may also be a carrier concentration effect by employing the more electropositive Ca.