Quasicrystals / Thermoelectric properties / Microstructure / Spark Plasma Sintering (SPS) / Al--Pd--Re Abstract. We report the thermoelectric properties of poly-grain Al--Pd--Re icosahedral quasicrystals and discuss an effect of improvement of their microstructure. The improvement of microstructure by using Spark Plasma Sintering (SPS) method resulted into a large increase of the electrical conductivity but less increase of the thermal conductivity. The relative density dramatically increased up to more than 90% by SPS. On the other hand, the microstructure itself does not have critical influence on the Seebeck coefficient, which is found to be strongly correlated with e=a (sample's compositions). Consequently, the dimensionless figure of merit (ZT) increased three times from 0.05 to 0.15.
Abstract. We report the thermoelectric properties of polygrain icosahedral Al--Pd--Mn quasicrystal and compare with those of (1/1, 2/1-)AlPdMnSi approximant crystals. To improve the dimensionless figure of merit (ZT), we substitute Ga for Al atoms in Al--Pd--Mn quasicrystal in accordance with the guiding principle of "weakly bonded rigid heavy clusters" (WBRHCs). Although the thermoelectric properties do not obey the WBRHCs principle, the maximum ZT increased by a factor of 1.4 from 0.18 for Al 71 Pd 20 Mn 9 to 0.26 for Al 68 Ga 3 Pd 20 Mn 9 quasicrystal.
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