Constitution, physical properties and thermodynamic modeling of the Hf-Mn system

Autor(en): Pavel Brož, Xinlin Yan, Vitaliy Romaka, Olga Fabrichnaya, Mario J. Kriegel, Vilma Buršíková, Jiří Buršík, Jan Vřešťál, Gerda Rogl, Herwig Michor, Ernst Bauer, Markus Eiberger, Andriy Grytsiv, Gerald Giester, Peter F. Rogl
Abstrakt: The Hf-Mn system is of a long-time interest due to the intermetallic Laves phase HfMn₂, a hydrogen storage material. Although this system has been experimentally investigated by several authors and critical reviews and thermodynamic modelling have been performed, there is still a lack of reliable information, particularly as the phase “HfMn” (sometimes labelled as "Hf₃Mn₂" or "Hf₂Mn") is suspected to be oxygen stabilized. This work includes a thorough investigation of the Hf-Mn phase equilibria employing diffusion zones, thermal analysis, powder and single crystal X-ray analyses, analytical electron microscopy as well as physical property studies of the Laves phase (magnetic susceptibility, specific heat, electrical resistivity and mechanical properties). The phase near “HfMn” was shown (TEM, WDX electron microprobe data, X-ray single crystal analysis) to be an oxygen stabilized phase with the formula Hf_3+xMn_3−xO_1−y (defect η-W₃Fe₃C type). Properties such as magnetic susceptibility/magnetization; 2–300 K, specific heat (2–1100 K), electrical resistivity (2–300 K) classify HfMn₂ as a metallic spin-fluctuation system with itinerant paramagnetism, originating from 3d states at Mn-sites and local moment paramagnetism of antisite Mn-atoms at Hf-sites. Mechanical properties (elastic moduli from density functional theory (DFT) and nanoindentation as well as hardness) group the Laves phase among rather hard and brittle intermetallics. DFT modeling revealed that Hf_3+xMn_3−x is thermodynamically unstable, but significant gains in enthalpy of formation arise from the inclusion of oxygen atoms, stabilizing the η phase. All phase diagram and DFT data together with the former literature information were used for the thermodynamic CALPHAD-type modelling of the Hf-Mn system.
Organisation(en): Institut für Materialchemie, Institut für Physikalische Chemie, Institut für Mineralogie und Kristallographie
Externe Organisation(en): Masaryk University, Technische Universität Wien, Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Technische Universität Bergakademie Freiberg, Czech Academy of Sciences, Universität Wien
Journal: Journal of Alloys and Compounds
Band: 976
ISSN: 0925-8388
DOI: https://doi.org/10.1016/j.jallcom.2023.173060
Publikationsdatum: 03-2024
Peer-reviewed: Ja
ÖFOS 2012: 104017 Physikalische Chemie
Schlagwörter
ASJC Scopus Sachgebiete: Mechanics of Materials, Mechanical Engineering, Metals and Alloys, Materials Chemistry
Link zum Portal: https://ucris.univie.ac.at/portal/de/publications/constitution-physical-properties-and-thermodynamic-modeling-of-the-hfmn-system(167ab5e8-bf77-46cc-b5be-3e2665045eaf).html

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