Short- and long-range ordering during the phase transition of the Zn6Sc 1/1 cubic approximant
2013 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 20, 205405- p.Article in journal (Refereed) Published
Using in situ x-ray scattering and synchrotron radiation, we have experimentally elucidated the mechanism of the cubic to monoclinic phase transition in the Zn6Sc 1/1 approximant to an icosahedral quasicrystal. The high-temperature cubic phase is described as a bcc packing of a large Tsai-type icosahedral cluster whose center is occupied by an orientationally disordered Zn-4 tetrahedron. A clear monoclinic distortion has been found to take place within 2 K around T-c = 157 K, in excellent agreement with the observed anomalies in the electrical resistivity and heat capacity. Also, a rapid variation of the super-structure reflection intensity is observed. The low-temperature monoclinic phase, as determined by single-crystal x-ray diffraction at 40 K, has been confirmed to consist of ordered Zn-4 tetrahedra, oriented in an anti-parallel way along the [(1) over bar 01] direction. Above T-c, a diffuse scattering signal is observed at the position of the super-structure reflections, which evidences that a short-range ordering of the Zn-4 tetrahedra takes place. In a way similar to a second-order phase transition, the correlation length describing this short-range ordering increases rapidly when the temperature diminishes and almost diverges when the temperature is close to T-c, going from 200 angstrom at 220 K to reach the very large value of 1200 angstrom at 161 K. Finally, using single-crystal x-ray diffraction, the atomic structure of the low-temperature monoclinic super-structure (space group C2/c) could be solved. The ordering of the Zn-4 tetrahedra is accompanied by a strong distortion of the surrounding shells.
Place, publisher, year, edition, pages
2013. Vol. 25, no 20, 205405- p.
Engineering and Technology Natural Sciences
IdentifiersURN: urn:nbn:se:uu:diva-201787DOI: 10.1088/0953-8984/25/20/205405ISI: 000318556100011OAI: oai:DiVA.org:uu-201787DiVA: diva2:629620