Publikationen

Physical properties of the ternary borides Ni21Zn2B20 and Ni3ZnB2

Autor(en)
Z. Malik, A. Grytsiv, H. Michor, G. Rogl, S. Puchegger, H. Mueller, M. Kriegisch, E. Bauer, C. Eisenmenger-Sittner, P. Rogl
Abstrakt

Mechanical, electrical and magnetic properties have been determined for the compounds Ni21Zn2B20 and Ni3ZnB2, which reveal a different boron-boron aggregation and bonding due to their different boron/metal ratio. Resonant Ultrasound Spectroscopy (RUS) measurements show significantly higher elastic moduli for Ni21Zn2B20 (E = 264 GPa) with a unique cluster of a cage of 20 B-atoms nesting a Ni-metal octahedron than for Ni3ZnB2 (E = 223 GPa), which contains covalently bonded B-B chain fragments consisting of 4 B-atoms. Similarly Vickers hardness (for a load of 200 ponds) is higher for Ni21Zn2B2 (HV = 6.87 GPa) than for Ni3ZnB2 (HV = 4.99 GPa). The higher boron/metal ratio for Ni21Zn2B20 is reflected in a smaller thermal expansion coefficient alpha = 8 x 10 x 10(-6) K-1 with respect to Ni3ZnB2 with alpha = 10.4 x 10(-6) K-1 (both determined for the range 150-250 K). At elevated temperatures, the specific heat C-p of both compounds, Ni21Zn2B20 and Ni3ZnB2, is clearly dominated by the lattice contribution. Analyses of C-p in terms of Debye and Einstein models indicate that the boron related high energy Einstein modes display at similar energies with spectral weights being in clear correspondence with their boron stoichiometries. Temperature dependent magnetization measurements reveal a paramagnetic behavior for both borides suggesting almost filled 3d states of Ni by contributions from B and Zn valence electrons. Electrical resistivities attest a dominant metallic behavior for both Ni21Zn2B20 and Ni3ZnB2 yielding negative Seebeck coefficients (electrons as the majority charge carriers) in the range of a few mu V/K. (C) 2012 Elsevier B.V. All rights reserved.

Organisation(en)
Institut für Physikalische Chemie, Fakultätszentrum für Nanostrukturforschung
Externe Organisation(en)
Universität Wien, Technische Universität Wien
Journal
Journal of Alloys and Compounds
Band
550
Seiten
302-307
Anzahl der Seiten
6
ISSN
0925-8388
DOI
https://doi.org/10.1016/j.jallcom.2012.09.122
Publikationsdatum
02-2013
Peer-reviewed
Ja
ÖFOS 2012
104017 Physikalische Chemie, 104011 Materialchemie, 103018 Materialphysik
Schlagwörter
Link zum Portal
https://ucris.univie.ac.at/portal/de/publications/physical-properties-of-the-ternary-borides-ni21zn2b20-and-ni3znb2(fb2d4937-5caa-44ae-a7cd-57685805e9fa).html