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Thin ribbons of stable icosahedral quasicrystal Al65Cu20Fe15 were irradiated with swift heavy ion (SHI) beam of 170 million electron volt (MeV) 58Ni+12 in high and clean vacuum environment at a temperature of 80 K to study the modification of its properties. Dynamic variation of resistance was studied on-line during and after irradiation for the first time, to understand the effect of SHI. The resistance decreased sharply at the time of incidence of ion beam due to creation of a large number of charge carriers by intense ionization by SHI and did oscillate around a mean value during irradiation due to defect creation and annihilation. The resistance increased rapidly just after the beam was stopped from its mean value during irradiation. The quasicrystalline peaks of the XRD data on these samples irradiated by SHI, were prominent till the ion beam fluence of 5 × 1012 particles/cm2, but the peak height consistently decreased with increasing fluence after a fluence of 1012 particles/cm2. © 2001 Elsevier Science Ltd. All rights reserved.

Physics

(SoNS) School of Natural Sciences

World University root node

Materials Research Bulletin

Modification of icosahedral quasicrystal Al65Cu20Fe15 by 170-MeV 58Ni+12 beam

The effect of 835 MeV Kr irradiation at 90 K on a stable icosahedral quasicrystal (Al65Cu25Fe5V5) is discussed here. A Kr-beam of this energy was chosen in order to keep the stopping power ∼1300 eV/Å in accordance with our previous work [Nucl. Instrum. Meth. B, 156 (1999) 201], while increasing the travelled path in which strong electronic excitations occur (≫sample thickness). The ratio ρ(φ)/ρ(0) {resistivity at fluence φ/resistivity at zero fluence} of quasicrystal goes through oscillatory changes, up to ∼1 × 1012 ions/cm2 where this ratio drops considerably. The ex situ XRD on the irradiated samples however shows the evidence of degradation of the structure after a critical fluence of 1 × 1011 ions/cm2. From the ex situ XRD measurements, this degradation does not seem to increase with further fluence up to φ = 1 × 1013 ions/cm2. © 2001 Elsevier Science Ltd. All rights reserved.

Solid State Communications

The observation of oscillatory behaviour in swift heavy ion irradiated quasicrystals

The effect of pure electronic excitations (by ∼ 835 MeV Kr irradiation) on a stable icosahedral quasicrystal is compared with the effect of electronic excitations combined with the nuclear collisions (by 100 MeV Ni irradiation) occurring in a similar quasicrystal. The critical stopping power was kept at 1300 eV/Å for both the experiments. Under the pure electronic excitations, the R(Φ))/R(0) [ratio of resistance at fluence Φ and the resistance on the same piece with zero fluence) of quasicrystal goes through oscillatory changes, until at ∼ 1 × 1012 ions/cm2 where this ratio drops considerably. The ex-situ XRD on the irradiated sample does show the evidence of degradation of the structure. In contrast, the Ni-irradiated sample shows an increase in resistivity after a critical fluence of 2.5 × 1013 ions/cm2, which remains constant for higher fluences. Corresponding defect annihilation effects are observed in the XRD of Ni-irradiated samples.