Icosahedral and stable decagonal quasicrystals in Ga46Fe23Cu23Si8, Ga50Co25Cu25 and Ga46V23Ni23Si8

During water quenching of the title alloys from the melt in fused silica tubes, the icosahedral quasicrystal (IQC) solidified first, then the decagonal quasicrystal (DQC) and finally the crystalline approximants. Both IQC and DQC phases disappeared after annealing at 730 degrees C. However, the DQC reappeared after a further annealing at 830 degrees C, but disappeared again after a second annealing at 730 degrees C. On heating, the differential thermal analysis curve showed a peak at about 800 degrees C, corresponding to the formation of the DQC from its approximants. These pieces of evidence prove that the DQC in these alloys is a stable phase above about 800 degrees C. The orientational relationship between them is: IQC fivefold axis//DQC tenfold axis//approximant [010].