Semi-metallic behaviour of i-AlCuFe quasicrystals

Theoretical prospective of quasicrystals as thermoelectric materials

“…This sensitivity to the sample stoichiometry is also observed in other transport parameters, like the Hall or Seebeck coefficients, and resembles doping effects in semiconductors. In addition, ͑i͒ the temperature dependence of the Seebeck coefficient: [5][6][7] is clearly nonlinear, exhibiting well-defined extrema in most instances, ͑ii͒ small variations in the chemical composition give rise to sign reversals in the S(T) value, ͑iii͒ for a given sample stoichiometry it shows a strong dependence on the heat treatments applied to the sample, 15 and ͑iv͒ S(T) has large values when compared to those of disordered metallic systems. 23 Therefore, the situation is quite different from that observed in amorphous materials, where the S(T) curve is dominated by electron diffusion yielding a linear temperature dependence.…”

“…In fact, a broad collection of different transport anomalies have been reported during the last decade, progressively leading to a condensed matter paradigm evolution for this new class of ordered structures. 3 Thus, anomalous behaviors in the temperature dependence of electrical conductivity, 4 Seebeck coefficient, [5][6][7] and thermal conductivity [8][9][10] strongly suggest that quasicrystalline alloys are marginally metallic and should be properly located at the border line between metals and semiconductors. 11 When considered from the perspective of current trends in the search for novel high performance thermoelectric materials ͑TEM's͒, 13 the peculiar position of these alloys is quite appealing.…”

Modeling the spectral conductivity ofAl−Mn−Siquasicrystalline approximants: A phenomenological approach

“…͑10͒. 42 Remarkably, nice fittings have been obtained in the context of twoband models by several groups. 24,43,44 Among them, only the model considered in Ref.…”

“…Thus, i-AlPdMn samples show a conductivity minimum located at about 40-60 K. 22 A less pronounced minimum is reached at lower temperatures ͑10-20 K͒ in the case of some i-AlCuFe samples. 6,23,24 In Fig. 2 we show the temperature dependence of the thermoelectric power for the same approximant phase.…”

“…This anomalous behavior resembles that observed for several icosahedral QCs belonging to the i-AlCu͑Fe, Ru͒ family. [24][25][26][27][28][29] …”