Growth and characterisation of single grain Al-Cu-Ru icosahedral quasicrystals from self-fluxes

ABSTRACT

In order to obtain high-quality single grains of the Al-Cu-Ru icosahedral quasicrystal (iQC), suitable for a structure analysis, the crystal growth conditions with the self-flux method have been studied. The melts of the master alloys with the compositions of Al_57.0+xCu_39.5-xRu_3.5 (x = 0, 2.5, 5, 7.5, 10) and Al_62.0Cu_34.0+y Ru_4.0-y (y = 0, 0.5, 1.5) were held at 1150°C for 2 h, then cooled down to 800, 900, or 1000°C at a rate of −2 K/h, and subsequently retained for various durations, up to 750 h. Single grain iQCs having several millimetre-sizes, which were evaluated their quality by powder X-ray diffraction (XRD), were grown throughout this study. The peak of (664004) reflection in powder XRD of the iQCs grown at 1000°C has approximately 50% narrower width than that grown at 800°C. The inhomogeneity of the compositions intra- as well as inter-grains grown at 800°C was observed. High-quality single grains with homogeneous composition could be achieved with a long-time annealing at 900°C or regardless of the annealing time at 1000°C. By changing the Al/Cu ratio of the master alloys, the composition could also be controlled for the iQCs grown at 1000°C. Single-crystal XRD experiment with synchrotron radiation on Al_66.6Cu_16.4Ru_17.0 iQC, grown at 1000°C, resulted in the collection of 2680 independent Bragg reflections that confirms the high-quality of the sample. The phase retrieval of the diffraction data resulted successfully in obtaining the structure solution, which reveals some characteristic features of this face-centred iQC structure.

KEYWORDS:

• Solution growth
• quasicrystals
• X-ray diffraction

Acknowledgements

We thank Akiji Yamamoto for his advice in the use of qcmem. We thank Ireneusz Buganski and Radoslaw Strzalka for their help in the use of SUPERFLIP. We thank Nobuyuki Miyazaki and Takashi Endo for their help in the use of JXA-8530 electron probe micro analyser, and Yurika Yamanouchi for her help in powder XRD experiment. This study has been supported by Material Analysis and Structure Analysis Open Unit (MASAOU). A part of this work was the result of using research equipment shared in MEXT Project for promoting public utilisation of advanced research infrastructure (Program for supporting introduction of the new sharing system) Grant Number JPMXS0420100419. H.T. acknowledges the financial support from JSPS KAKENHI Grant Numbers JP19K04982, JP19H05817, JP19H05819.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by JSPS KAKENHI [grant numbers JP19K04982, JP19H05817, JP19H05819].