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Title: Rare-earth transition-metal intermetallics: Structure-bonding-property relationships

Abstract

The explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding property relationships. The work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe 13-xSi x system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn{sub 13}-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides Re 2-xFe 4Si 14-y and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi 2: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb 3Zn 3.6Al 7.4: Partially ordered structure of Tb 3Zn 3.6Al 7.4 compound provides new insightsmore » into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn 39(Cr xAl 1-x) 81: These layered structures are similar to icosahedral Mn-Al quasicrystalline compounds. Therefore, this compound may provide new insights into the formation, composition and structure of quasicrystalline materials.« less

Authors:
 [1]
  1. Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Lab., Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
882892
Report Number(s):
IS-T 2306
TRN: US200623%%544
DOE Contract Number:
W-7405-Eng-82
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BONDING; ELECTRONIC STRUCTURE; IRON SILICIDES; OPENINGS; SYNTHESIS; TRANSFORMATIONS; TRANSITION ELEMENTS; ZINC

Citation Formats

Han, M. K. Rare-earth transition-metal intermetallics: Structure-bonding-property relationships. United States: N. p., 2006. Web. doi:10.2172/882892.
Han, M. K. Rare-earth transition-metal intermetallics: Structure-bonding-property relationships. United States. doi:10.2172/882892.
Han, M. K. Sun . "Rare-earth transition-metal intermetallics: Structure-bonding-property relationships". United States. doi:10.2172/882892. https://www.osti.gov/servlets/purl/882892.
@article{osti_882892,
title = {Rare-earth transition-metal intermetallics: Structure-bonding-property relationships},
author = {Han, M. K.},
abstractNote = {The explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding property relationships. The work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe13-xSix system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn{sub 13}-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides Re2-xFe4Si14-y and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi2: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb3Zn3.6Al7.4: Partially ordered structure of Tb3Zn3.6Al7.4 compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn39(CrxAl1-x)81: These layered structures are similar to icosahedral Mn-Al quasicrystalline compounds. Therefore, this compound may provide new insights into the formation, composition and structure of quasicrystalline materials.},
doi = {10.2172/882892},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Thesis/Dissertation:
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  • Our explorations of rare-earth, transition metal intermetallics have resulted in the synthesis and characterization, and electronic structure investigation, as well as understanding the structure-bonding-property relationships. Our work has presented the following results: (1) Understanding the relationship between compositions and properties in LaFe 13-xSi x system: A detailed structural and theoretical investigation provided the understanding of the role of a third element on stabilizing the structure and controlling the transformation of cubic NaZn 13-type structures to the tetragonal derivative, as well as the relationship between the structures and properties. (2) Synthesis of new ternary rare-earth iron silicides RE 2-xFe 4Si 14-ymore » and proposed superstructure: This compound offers complex structural challenges such as fractional occupancies and their ordering in superstructure. (3) Electronic structure calculation of FeSi 2: This shows that the metal-semiconductor phase transition depends on the structure. The mechanism of band gap opening is described in terms of bonding and structural distortion. This result shows that the electronic structure calculations are an essential tool for understanding the relationship between structure and chemical bonding in these compounds. (4) Synthesis of new ternary rare-earth Zinc aluminides Tb 3Zn 3.6Al 7.4: Partially ordered structure of Tb 3.6Zn 13-xAl 7.4 compound provides new insights into the formation, composition and structure of rare-earth transition-metal intermetallics. Electronic structure calculations attribute the observed composition to optimizing metal-metal bonding in the electronegative (Zn, Al) framework, while the specific ordering is strongly influenced by specific orbital interactions. (5) Synthesis of new structure type of Zn 39(Cr xAl 1-x) 81: These layered structures are similar to icosahedral Mn-Al quasicrystalline compounds. Therefore, this compound may provide new insights into the formation, composition and structure of quasicrystalline materials.« less
  • The effects of hydrogen absorption on the magnetic and structural properties of several rare earth - transition metal intermetallics were studied. The systems which were studied are: Th/sub 7/Co/sub 3/, Th/sub 7/Ni/sub 3/, CeNi/sub 4/Al, Th/sub 6-x/Y/sub x/Mn/sub 23/, R/sub 6/Mn/sub 23/ (R = Gd, Tb, Dy, Ho and Er), Gd/sub x/Y/sub 6-x/Fe/sub 23/ and Er/sub x/ Y/sub 6-x/Fe/sub 23/. The major findings obtained regarding each of these systems are discussed briefly.
  • DC resistivity, dc magnetization, and specific heat of eight Sc{sub 5}Co{sub 4}Ge{sub 10}-type crystal-structure compounds R{sub 5}T{sub 4}Ge{sub 10} for R = Dy, Ho, Er, Tm, and T = Rh and Ir are presented. The resistivity, single-crystal magnetization, and specific-heat results show that in all those compounds, the magnetic moments order antiferromagnetically in the c direction at low temperature. However, in the Er and Tm compounds, the magnetizations along x-y hard directions do not show any anomalies above 2.0 K. This suggests that the ordered Er and Tm ions, which have positive quadrupole coefficients, interact with a crystal field thatmore » has an electronic potential valley along the c axis. The fitting of the hard axis magnetizations to Curie-Weiss law suggests that the resulting antiferromagnetic-like {theta} reflects the strength of the crystal-field torque on the magnetic moments rather than the strength of antiferromagnetic exchange.« less
  • A systematic study of the superconducting and normal state properties of some ternary rare earth transition metal silicides and germanides of the Sc/sub 5/Co/sub 4/Si/sub 10/0-type is reported. Low temperature heat capacity measurements indicate the presence of a complicated phonon density of states in these structurally complex compounds. A better description of the phonon spectrum of the high T/sub c/ materials Sc/sub 5/Rh/sub 4/Si/sub 10/, Sc/sub 5/Ir/sub 4/Si/sub 10/, and Y/sub 5/Os/sub 4/Ge/sub 10/, given by a model proposed by Junod et al., is presented and discussed. The large values of ..delta..C/..gamma../sub n/T/sub c/ and the electron-phonon coupling constant formore » these high T/sub c/ compounds indicate that they are strong-coupled superconductors. Relative to other ternary superconductors, many of these materials have large Debye temperatures. DC electrical resistivity measurements on these compounds show resistivity behavior deviating from those exhibited by simple metals. The rho(T) data for Y/sub 5/Ir/sub 4/Si/sub 10/, Lu/sub 5/Ir/sub 4/Si/sub 10/, and Y/sub 5/Os/sub 4/Ge/sub 10/, indicate the presence of anomalies. Static molar magnetic susceptibility measurements performed on these compounds indicate (1) a small effective magnetic moment of 0.26..mu../sub B/ on the Co atom and (2) anomalous behaviors in the Lu/sub 5/Rh/sub 4/Si/sub 10/, Lu/sub 5/Ir/sub 4/Si/sub 10/, Y/sub 5/Ir/sub 4/Si/sub 10/, Lu/sub 5/Ir/sub 4/Ge/sub 10/, and Y/sub 5/Rh/sub 4/Ge/sub 10/ data. Lastly, upper critical magnetic field measurements were performed on Sc/sub 5/Co/sub 4/Si/sub 10/, Sc/sub 5/Rh/sub 4/Si/sub 10/, Sc/sub 5/Ir/sub 4/Si/sub 10/, Lu/sub 5/Rh/sub 4/Si/sub 10/, Lu/sub 5/Ir/sub 4/Si/sub 10/, and Y/sub 5/Os/sub 4/Ge/sub 10/.« less