Transport properties of the doped thermoelectric material /spl beta/-K/sub 2/Bi/sub 8/Se/sub 13/

The synthesis, physicochemical, spectroscopic, and structural characterization of the compounds /spl beta/-K/sub 2/Bi/sub 8/Se/sub 13/, K/sub 2/Sb/sub 8/Se/sub 13/, K/sub 2.5/Bi/sub 8.5/Se/sub 14/, and K/sub 2.5/Sb/sub 8.5/Se/sub 14/ have been previously reported and show promising properties for thermoelectric applications. While /spl beta/-K/sub 2/Bi/sub 8/Se/sub 13/ is isostructural with K/sub 2/Bi/sub 7/S/sub 13/, the isostructural K/sub 2.5/Bi/sub 8.5/Se/sub 13/ and K/sub 2.5/Sb/sub 8.5/Se/sub 14/ are different but have similar structural features to /spl beta/-K/sub 2/Bi/sub 8/Se/sub 13/. Compared with /spl alpha/-K/sub 2/Bi/sub 3/Se/sub 13/, which has a room temperature electrical conductivity of 2 S/cm and a Seebeck coefficient ranging from -210 to -260 /spl mu/V/K, /spl beta/-K/sub 2/Bi/sub 8/Se/sub 13/ shows excellent electrical conductivity values at room temperature while maintaining high Seebeck coefficients. In this work the doping of the homologous compound /spl beta/-K/sub 2/Bi/sub 8/Se/sub 13/ was explored by employing varying concentrations of different dopants. Where possible, transport measurements were carried out on both single crystal and polycrystalline ingot material. From these data the trends in the key parameters were identified for optimizing the power factor and figure of merit.