Structure and Properties of Intermetallic Ternary Rare Earth Compounds PDF Download
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Author: Frederick Casper
Publisher:
ISBN:
Category :
Languages : en
Pages : 127
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Book Description
Author: Frederick Casper
Publisher:
ISBN:
Category :
Languages : en
Pages : 127
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The so called material science is an always growing field in modern research. For the development of new materials not only the experimental characterization but also theoretical calculation of the electronic structure plays an important role. A class of compounds that has attracted a great deal of attention in recent years is known as REME compounds. These compounds are often referred to with RE designating rare earth, actinide or an element from group 1 - 4, M representing a late transition metal from groups 8 - 12, and E belonging to groups 13 - 15. There are more than 2000 compounds with 1:1:1 stoichiometry belonging to this class of compounds and they offer a broad variety of different structure types. Although many REME compounds are know to exist, mainly only structure and magnetism has been determined for these compounds. In particular, in the field of electronic and transport properties relatively few efforts have been made. The main focus in this study is on compounds crystallizing in MgAgAs and LiGaGe structure. Both structures can only be found among 18 valence electron compounds. The f electrons are localized and therefor not count as valence electrons. A special focus here was also on the magnetoresistance effects and spintronic properties found among the REME compounds. An examination of the following compounds was made: GdAuE (E = In, Cd, Mg), GdPdSb, GdNiSb, REAuSn (RE = Gd, Er, Tm) and RENiBi (RE = Pr, Sm, Gd - Tm, Lu). The experimental results were compared with theoretic band structure calculations. The first half metallic ferromagnet with LiGaGe structure (GdPdSb) was found. All semiconducting REME compounds with MgAgAs structure show giant magnetoresistance (GMR) at low temperatures. The GMR is related to a metal-insulator transition, and the value of the GMR depends on the value of the spin-orbit coupling. Inhomogeneous DyNiBi samples show a small positive MR at low temperature that depends on the amount of metallic impurities. At higher field.
Author: Andrej Szytula
Publisher: CRC Press
ISBN: 0429607318
Category : Science
Languages : en
Pages : 294
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Book Description
Rare-earth intermetallics, also known as lanthanide elements, play an important role in the study of magnetic materials and the development of semi- and super-conducting materials. This handbook provides an up-to-date compilation of crystallographic, physical, and magnetic data on rare-earth intermetallic compounds. Over 20 different structure types are described in detail with an emphasis on how crystal structure can affect magnetic properties. Theoretical models for magnetic interactions are described as well as the impact of crystal electric fields on transport properties, magneto crystalline anistropy and hyperfine interactions. This book provides materials scientists, engineers and physicists with all the critical information needed to use rare-earth intermetallics effectively in the development of new materials.
Author: Riccardo Freccero
Publisher: Springer Nature
ISBN: 3030589927
Category : Technology & Engineering
Languages : en
Pages : 221
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Book Description
The thesis focuses on the syntheses, structural characterizations and chemical bonding analyses for several ternary R–M–Ge (R = rare earth metal; M = another metal) intermetallics. The challenges in understanding the main interactions governing the chemistry of these compounds, which lead to our inability to predict their formation, structure and properties, are what provided the motivation for this study. In particular, the R2MGe6 (M = Li, Mg, Al, Cu, Zn, Pd, Ag), R4MGe10-x (M = Li, Mg), R2Pd3Ge5, Lu5Pd4Ge8, Lu3Pd4Ge4 and Yb2PdGe3 phases were synthesized and structurally characterized. Much effort was put into the stabilization of metastable phases, employing the innovative metal flux method, and into the accurate structure solution of twinned crystals. Cutting-edge position-space chemical bonding techniques were combined with new methodologies conceived to correctly describe the Ge–M, Ge–La and also La–M polar-covalent interactions for the La2MGe6 (M = Li, Mg, Al, Cu, Zn, Pd, Ag) series. The present results constitute a step forward in our comprehension of ternary germanide chemistry as well as providing a good playground for further investigations.
Author: B. J. Gibson
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Rainer Pöttgen
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110636727
Category : Science
Languages : en
Pages : 324
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Book Description
The expanded edition focuses still more on Synthesis discussing necessary requirements for sample preparation and presents the broad range from structural analysis to property investigations. Additional examples of chemical and physical properties are highlighted for metallic, binary and multinary intermetallic compounds. The work contains an up-dated literature overview in all sub-chapters and a detailed formulae index.
Author: K.A. Gschneidner
Publisher: Elsevier
ISBN: 9780444513236
Category : Science
Languages : en
Pages : 688
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Book Description
This volume of the Handbook illustrates the rich variety of topics covered by rare earth science. Three chapters are devoted to the description of solid state compounds: skutterudites (Chapter 211), rare earth -antimony systems (Chapter 212), and rare earth-manganese perovskites (Chapter 214). Two other reviews deal with solid state properties: one contribution includes information on existing thermodynamic data of lanthanide trihalides (Chapter 213) while the other one describes optical properties of rare earth compounds under pressure (Chapter 217). Finally, two chapters focus on solution chemistry. The state of the art in unraveling solution structure of lanthanide-containing coordination compounds by paramagnetic nuclear magnetic resonance is outlined in Chapter 215. The potential of time-resolved, laser-induced emission spectroscopy for the analysis of lanthanide and actinide solutions is presented and critically discussed in Chapter 216.
Author: Mi-Kyung Han
Publisher:
ISBN:
Category :
Languages : en
Pages : 452
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Book Description
The purpose of this thesis is to explore novel rare-earth, transition metal compounds and to investigate their structure and bonding and how these influence their properties. We have focused on the synthesis, characterization and electronic structure investigations, as well as physical properties of ternary rare-earth Fe-rich intermetallics, e.g., LaFe[subscript 13-x]Si[subscript x], and RE[subscript 2-x]Fe4Si[subscript 14-y], etc. The LaFe[subscript 13-x]Si[subscript x], (1.0 [equal to or less than] x [equal to or less than] 5.0) compounds with structures related to the cubic NaZn13−type are an important series of compounds to study for possible efficient magnetic refrigeration. A systematic structural study of the compositional variation in LaFe[subscript 13-x]Si[subscript x], exhibits a structural transformation from the cubic NaZn13−structure type to a tetragonal derivative due to preferential ordering of Fe and Si atoms. Temperature-dependent single crystal X-ray diffraction at various temperatures and electronic structure calculations (both Extended Hückel and TB-LMTO) was performed on the cubic phases to examine the origin of the large magnetic entropy change. The giant magnetocaloric effect of cubic LaFe[subscript 13-x]Si[subscript x] alloys results from coupling between magnetic ordering and structural transformation. In light of the potential superstructures that could be observed for RE[subscript 2-x]Fe4Si[subscript 14-y] as well as possible modifications of semiconducting [Beta]-FeSi2, we report herein a thorough examination of the chemical composition and structure of RE[subscript 2-x]Fe4Si[subscript 14-y] (RE = Y, Gd-Lu) using a combination of electron microscopy and X-ray diffraction, and demonstrate a new superstructure for this class of compound. The structures are built up of rare-earth silicide planes with approximate compositions "RE1.2Si1.9" alternating with [Beta]-FeSi2-derived (hkl)-type slabs. Investigation by transition electron microscopy (TEM) reveals a superstructure in the crystallographic ab-plane. Fe Mössbauer spectra confirm two different iron environments in superstructure. Magnetic susceptibilities suggest weak magnetic coupling between rare-earth elements, and resistance measurements indicate poor metallic behavior with a large residual resistivity at low temperatures, which is consistent with disorder. Electronic structure calculations on model structures identify a pseudogap in the densities of states for specific valence electron counts that helps to provide a useful electron counting scheme for this class of rare-earth/transition metal/main group compound.
Author:
Publisher:
ISBN: 9781109249088
Category : Germanides
Languages : en
Pages :
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Book Description
The aspects of composition, structure-bonding, and properties, along with the reasons governing the formation of one phase over another all still, quite surprisingly remain an open question concerning intermetallic compounds. This work was therefore inspired by a need to better understand the above-mentioned characteristics for several binary and ternary rare-earth (RE) germanides. The structure and properties discussed herein, report the crystal chemistry and physical properties associated with over 40 new binary and ternary intermetallic compounds synthesized from their respective elements using either classical solid state reactions or by the metal flux growth technique. All contain the Group 14 element Ge along with several of the lanthanide f-block metals (commonly referred to as rare-earths) which represent the majority of the binary compounds while the ternary compounds include the additional combination of select s - and p -block metals and semi-metals - Mg, Ca, In, Sn. Their crystal structures and compositions were determined using a number of techniques including single-crystal and powder X-ray diffraction, electron diffraction and electron microscopy. Along with the structure and bonding, this dissertation devotes a discussion to the physical properties which are exhibited by these compounds as a function of temperature or magnetic field in association with their bulk magnetic susceptibility, electrical resistivity and heat-capacity. The results from these along with certain similarities in their structure and bonding allows for the classification of five families organized based on their chemical formulae which include the following: (1) RE 5-x Mg x Ge 4 (RE = Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) containing two types of Ge-Ge dimers of which their bonding can be affected by small changes in the overall composition; (2) RE 2 InGe2 (RE = Sm, Gd, Tb, Dy, Ho, and Yb) containing [Ge 2] dimers connected with four-coordinated In atoms which results in planar InGe 2 layers; (3) RE Sn 1+x Ge1-x (RE = Y, Gd, Tb, Dy, Ho, Er, Tm), RE 2 [Sn x Ge 1-x] 5 (RE = Nd, Sm), RE [Sn x Ge 1-x]2 (RE = Gd, Tb), which uniquely contain two group 14 elements Ge and Sn that are found to preferentially occupy specific crystallographic sites - these being infinite zig-zag chains of Germanium and square sheets of Sn; (4) RE 3 Ge 4 (RE = Gd, Tb, Dy, Ho, Er, Tm, and Y) containing fused fragments of two-bonded zig-zag Germanium atoms; (5) RE 3 Ge 5 (RE = Sm, Gd, Tb, Dy) an example of polymorphism with two dimensional and three dimensional anionic sub-networks with different orientations of zig-zag chains of Germanium.
Author:
Publisher: Elsevier
ISBN: 0444641580
Category : Science
Languages : en
Pages : 372
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Book Description
Handbook on the Physics and Chemistry of Rare Earths: Including Actinides, Volume 53, is a continuous series covering all aspects of rare earth science, including chemistry, life sciences, materials science and physics. The book focuses on rare earth elements [Sc, Y, and the lanthanides (La through Lu], but when relevant, information is included on the related actinide elements. Individual chapters are comprehensive, up-to-date, critical reviews written by highly experienced, invited experts, with this release including chapters on a Comparison of the Electronic Properties of Lanthanides with Formally Isoelectronic Actinides, Redox catalysis with redox-inactive rare-earth ions in artificial photosynthesis, and more. The series, which was started in 1978 by Professor Karl A. Gschneidner Jr., combines, and integrates, both the fundamentals and applications of these elements with two published volumes each year. Presents up-to-date overviews and new developments in the field of rare earths, covering both their physics and chemistry Contains Individual chapters that are comprehensive and broad, with critical reviews Provides contributions from highly experienced, invited experts
