Preparation and electrical properties of aluminium-based ternary and quaternary quasi-crystals

An addition of a small amount of silicon, ruthenium, molybdenum or niobium to AlMn and AlV alloy systems (manganese has a magnetic moment while vanadium has not) causes a decrease in the amount of second phase, sharpening of the X-ray diffraction peaks and an increase in the crystallization temperature. The electrical resistivities of the quasi-crystalline AlMn alloys are 800–1000 μΩ cm and have negative temperature coefficients from 1 K to room temperature. Such high resistivities must be due to an extremely short mean free path of the electrons. In the low temperature region (less than 50 K), the resistivity π of the quasi-crystalline AlMn alloys increases rapidly with decreasing temperature T. The resistivity is proportional to −log T or T^−a on the higher temperature side of this region and to −T^1/2 on the lower side. In contrast, π for the quasicrystalline Al-V alloys is 200–400 μΩ cm and is nearly constant from 1 k to 77 K. The behaviour of the resistivity for quasi-crystalline Al-Mn and Al-V alloys cannot be simply interpreted by ordinary mechanisms. Attempts have been made to interpret the behaviour by tunnelling and variable-range hopping conduction in the critical but not extended or localized states which are considered to be the characteristic electronic states in quasi-crystals.