Chemical bonding and electronic-structure in MAX phases as viewed by X-ray spectroscopy and density functional theory

Martin Magnuson, Maurizio Mattesini
  • Thin Solid Films, January 2017, Elsevier
  • DOI: 10.1016/j.tsf.2016.11.005

Chemical bonding and electronic structure in MAX-phases

What is it about?

The MAX-phases combines the best combinations of ceramics and metals. Bulk construction materials are made by a powder metallurgical process at high pressure and temperature (sintering). Parts of combustion engines, rockets and heating elements Thin films and surface coatings are made by building up individual atomic layers (sputtering). Cutting tools, electrical switches, and diffusion barriers It is important that single crystal material (thin film) is employed in order to understand and obtain the basic physical properties The target of the research is to understand and systematize how the underlying electronic structure and chemical bonding affects the macroscopic properties

Why is it important?

Generally, there are three different types of bonding; relatively weak M 3d – A 3p bonding close to the Fermi level, as well as M 3d - C 2p and M 3d – C 2s bonds, that are stronger and deeper in energy than the Fermi level. The electronic structure and chemical bonding are significantly different in the nitrides than in the isostructural carbides. A modification of the chemical bond strengths can also be achieved by exchanging the A-element which results in a change of the valence electron population (e.g., Al to Si, and Ge in MAX-phases) or changing the crystal structure (211 to 312, 413). This means that the chemical bond length/strength and materials properties can be tailored for specific applications.

Perspectives

Associate Prof. Martin Magnuson (Author)
Department of Physics, Chemistry and Biology (IFM)

The anisotropic Seebeck coefficient observed in single-crystal Ti3SiC2 will be further explored in other MAX-phase systems. The potential for magnetism in MAX phases is an important issue and an active field of research since this would add a new property to a large number of phases that can be useful in various applications. More information on the use of X-ray spectroscopy and MAX-phases is available at: https://people.ifm.liu.se/marma/ and http://martinmagnuson.com/ Thin Solid Films. 621, 108-130 (2017)

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http://dx.doi.org/10.1016/j.tsf.2016.11.005

The following have contributed to this page: Associate Prof. Martin Magnuson