Synthesis and Thermoelectric Properties of the Clathrate-I Phase K^sub 8^Li^sub x^Ge^sub 44-x/4^^sub 2-3x/4

Thermoelectric transport properties at temperatures below 300 K were determined for clathrate-I phases K^sub 8^Li^sub x^Ge^sub 44-x/4^^sub 2-3x/4^ ( denotes a vacancy) with compositions 0.25 [less than or equal to] x [less than or equal to] 2.7. Samples were prepared by solid-state reaction and compacted by spark plasma sintering. The lattice constants and chemical composition of the samples were investigated by x-ray powder diffraction and wavelength dispersive x-ray spectroscopy, respectively. Depending on composition, the temperature dependence of the electrical resistivity is metal or semiconductor-like. Absolute value of the negative Seebeck coefficient (n-type conductivity) increased linearly with temperature. All samples had low thermal conductivity of 1-1.5 W m^sup -1^ K^sup -1^ at 300 K.