Novel compounds in the Sc-rich part of the systems Sc-{Co,Pd,Pt}-Ga: Structure and bonding
- Author(s)
- V.V. Romaka, Gerda Rogl, J. Buršík, A. Grytsiv, G. Giester, P. Rogl
- Abstract
The present paper comprises a detailed structural analysis of two novel compounds in the Sc-Co-Ga system: τ3-Sc50Co13Ga3 (space group Fm-3; ε-Mg26-xAg7+x type), and τ4-Sc6Co1.73+x+yGa1-x (space group Immm; x=0.43; y=0.14; Ho6Co2Ga derivative type). Although alloys in the isothermal section are oxygen-free, the alloy of τ3, prepared for single crystal growth via partial melting in an alumina crucible, contained a minor amount of oxygen and can be considered as oxygen-stabilized Sc50Co13Ga3O1.1 (WDX-data). A search for homologous compounds in the systems Sc-{Pd,Pt}-Ga prompted the existence of two compounds Sc54{Pd,Pt,Ga}17, which from X-ray single crystal analyses proved both to be isotypic with the Hf54Os17-type structure (space group Immm). Whereas Sc54(Pd0.652Ga0.348)17 has a very limited homogeneity region at 850°C, Sc54(Pt1-xGax)17 exhibits at 850°C a large homogeneity region (0<x<0.28) extending from Ga-rich Sc76Pt17.2Ga6.8≡Sc54(Pt0.72Ga0.28)17 to novel binary Sc54Pt17. Interestingly, against the usual trend of solution hardening, hardness, Young's modulus and fracture toughness all decrease with increasing Ga-content: this effect is less pronounced for Sc54(Pd1-xGax)17 than for Sc54(Pt1-xGax)17 and is in line with DFT calculations indicating a weakening of bonding with increasing Ga content, thereby overcompensating the solution hardening effect. DFT modeling showed a common bonding feature for all the studied compounds – a strong electron localization inside the Sc6 octahedra, stacking of which leads to the formation of Mackay icosahedra in Sc54(Pd1-xGax)17, Sc54(Pt1-xGax)17, and Sc50Co13Ga3. The band structure of Sc6Co2.25Ga0.625 and Sc50Co13Ga3 indicates their metallic behavior, while Sc54(Pd1-xGax)17 and Sc54(Pt1-xGax)17 show distinct semimetal features. All investigated compounds in this work show similar trends in Bader charge distribution with a positively charged Sc-sublattice and a negatively charged sublattice formed by transition metals (Co, Pd, Pt) and Ga.
- Organisation(s)
- Department of Materials Chemistry, Department of Mineralogy and Crystallography
- External organisation(s)
- Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Czech Academy of Sciences
- Journal
- Journal of Alloys and Compounds
- Volume
- 998
- Pages
- 1-18
- No. of pages
- 18
- ISSN
- 0925-8388
- DOI
- https://doi.org/10.1016/j.jallcom.2024.174864
- Publication date
- 09-2024
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105116 Mineralogy, 105113 Crystallography, 104017 Physical chemistry
- Keywords
- ASJC Scopus subject areas
- Mechanics of Materials, Mechanical Engineering, Metals and Alloys, Materials Chemistry
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/novel-compounds-in-the-scrich-part-of-the-systems-sccopdptga-structure-and-bonding(e971ad67-0c23-4f39-a81a-fa9f1f228b69).html