Effects of the addition of Co on the thermoelectric properties of the AlPdMn quasicrystalline system

Partially due to their lack of periodic structure, quasicrystals have inherently low thermal conductivity, on the order of 1-3 W/mK. AlPdMn quasicrystals exhibit reasonable values of electrical conductivity (500-800 (/spl Omega//spl middot/cm/sup -1/)) and thermopower (80 /spl mu/V/K) with respect to thermoelectrics. In an effort to further increase the thermopower and hopefully decrease the thermal conductivity via phonon scattering, a fourth element was added to the nominally Al/sub 70/Pd/sub 10/Mn/sub 10/ quasicrystal. X-ray data confirms that the addition of the additional element does not alter the quasiperiodicity of the sample. Several Al/sub 70/Pd/sub 22.5/Mn/sub 7.5/ quasicrystal ingots were grown. Two subsequent batches of Al/sub 70/Pd/sub 22.5/5Mn/sub 7.5/ were grown, adding up to 2% Co. Thermopower, electrical conductivity, and thermal conductivity were measured on each sample over a broad temperature range and the results are discussed.