Electrical and thermal transport properties of icosahedral Al70Pd22.5(Re1−xMnx)7.5 quasicrystals
This work presents measurements of the electrical resistivity (ρ), Seebeck coefficient, and thermal conductivity (κ) of icosahedral Al70Pd22.5(Re1−xMnx)7.5 quasicrystals from 10to300K. A series of quasicrystals was prepared with x=0, 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, and 1.0 to systematically study the effect of substitution. The electrical resistivity increases as the temperature decreases, suggesting a semiconductinglike behavior in these alloys. The room-temperature values of the Seebeck coefficient vary from −5μV∕K to +65μV∕K, showing a significant dependence on the value of x. However, κ exhibits a rather weak composition dependence in the temperature range investigated. The room-temperature dimensionless thermoelectric figure of merit (ZT) of this system is optimized at x=0.1. With further appropriate heat treatments, high ZT is presumably available at elevated temperatures in the Al70Pd22.5(Re0.9Mn0.1)7.5 sample.
Transport properties of icosahedral quasicrystal Al72Pd19.5Mn8.5
Abstract We present measurements of the thermoelectrical properties of polygrain icosahedral quasicrystal Al 72 Pd 19.5 Mn 8.5 in the temperature range 10–300 K. Electrical resistivity has a relatively low room temperature value, ρ R.T. =1.2 mΩ cm, by lowering the temperature it shows an increase with a maximum value at 120 K. Thermoelectric power is positive in the whole temperature ranges with a quite high room temperature value, S R.T. =70 μV/K. Thermal conductivity shows a maximum at 30 K, and a broad minimum around 125 K. The room temperature value is K R.T. =3.4 W/mK. The appearance of the maximum in thermal conductivity at 30 K comes mainly from structural scattering, while at temperatures above 120 K from the contribution of the localized phonon state.
Semi-metallic behaviour of i-AlCuFe quasicrystals
We report on new measurements of the electrical conductivity, Hall effect and thermoelectric power in the temperature range from 2 K to 440 K for AlCuFe quasicrystals of different compositions and annealing treatments. Particularly, the Hall coefficient and the thermopower show a strong dependence on composition and also on heat treatment. The increase of sample perfection on annealing between 810° C and 825° C is demonstrated by analysing X-ray measurements.All measured quantities can be explained in terms of a semimetal containing both electrons and holes at low temperatures, at least for samples near the ideal quasicrystalline structure and composition.