Gille, Peter; Bauer, Birgitta; Hahne, Michael; Smontara, Ana; Dolinšek, Janez
Single crystal growth of Al-based intermetallic phases being approximants to quasicrystals.
In: Journal of Crystal Growth, Vol. 318, No. 1: pp. 1016-1020
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Decagonal (d) quasicrystals are formed in a number of Al-based ternarysystems with d-AlCoNi being the best studied decagonal phase. They arehighly anisotropic showing unusual properties of e.g. electric andthermal transport when measured along the periodic or quasiperiodicdirections. For a long time, this has been attributed to the lack ofperiodicity in certain crystallographic orientations. Some neighbouringphases in the Al-Co-Ni system as well as in related ternaries consist ofthe same type of large icosahedral clusters, but are periodic in allthree directions, sometimes with very large unit cells. Therefore, theyare called approximants to the decagonal quasicrystals. They allowcomparative studies of these phases as to judge whether some unusualproperties of quasicrystals arise from the lack of periodicity or fromthe common atomic arrangements. Additional to decagonal AlCoNiquasicrystals, various approximants (monoclinic Al(13)(Co,Ni)(4),orthorhombic Al(13)CO(4), orthorhombic Al(4)(Cr,Fe), monoclinicAl(13)Fe(4) and its ternary extensions Al(13)(Fe,Cr)(4) andAl(13)(Fe,Ni)(4)) were grown by the Czochralski method as large singlecrystals as to carry out transport orientation-dependent measurements.It could be found that transport properties show remarkably similaranisotropic features when comparing corresponding crystallographicdirections in these phases that can be related to the periodic stackingof layers.