Characteristic chemical shift of quasicrystalline alloy Al₅₃Si₂₇Mn₂₀ studied by EELS and SXES

Abstract

Chemical shifts of all constituent atoms for amorphous (Am), quasicrystalline (QC) and crystalline (Cryst) alloys of Al 53 Si 27 Mn 20 were investigated for the first time by high energy-resolution electron energy-loss spectroscopy (EELS) and soft-X-ray emission spectroscopy (SXES). Among Al L-shell excitation EELS spectra of Am, QC and Cryst alloys, only QC alloy showed an apparent chemical shift to the larger binding energy side by 0.4 eV. In Al-K and Si-K emission SXES spectra of these alloys, only QC alloy showed a chemical shift to the larger binding energy side by 4 eV for Al-K and 6 eV for Si-K . These chemical shift values are comparable to those of corresponding metal oxides. This indicates a smaller amount of valence charge at Al and Si atomic sites in QC alloy. On the other hand, Mn-L SXES spectra did not show any chemical shift. Therefore, the decreased charge from Al and Si sites should be distributed between atomic sites, indicating the presence of covalent bonding nature for QC ordered alloy.

Amount of valence charge of Al- and Zn-based quasicrystals and related approximant crystals evaluated by chemical shift observations and Bader analysis

“…These results suggest that the amount of valence charge of Al atoms in those quasicrystalline alloys is decreased, but that of approximant alloy is comparable with that of pure aluminium. The present result and those reported previously of chemical shift observed for Al-Kα and Zn-L emissions[4,5,8] are listed inTables 1 and 2, respectively. The results of reference materials of α-Al 2 O 3 and ZnO obtained at the same experimental conditions are also shown.…”

“…The decreased charges were evaluated to be 1.2 and 1.1 ± 0.3 e -/atom for F-type and P-type quasicrystalline materials, respectively. The observed chemical shifts of all constituent atoms for quasicrystalline materials by EELS and SXES [4,5,8] were positive. It can be said that the electron charge at all atomic sites is decreased.…”

“…Reported results on chemical shifts for Al-Si-Mn (amorphous, quasicrystalline and crystalline materials) [4], Al-Re-Si approximant (1/1-covalent, 1/1-metallic and 1/0-metallic materials) [8] and Zn-Mg-Zr (P-type and F-type quasicrystals and approximant crystals) [5], and the present experimental outcomes on Al-Pd-Cr-Fe alloys were used for evaluating the valence charge amount. Furthermore, experiments on Al-Pd-Cr-Fe intermetallic compounds were done as follows.…”

“…Characteristic chemical shifts of all constituent atoms of Al-Si-Mn and Zn-Mg-Zr quasicrystalline and related crystalline materials have been reported by EELS and soft-X-ray emission spectroscopy (SXES) experiments [4,5]. Only quasicrystalline materials showed apparent positive chemical shifts.…”