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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.
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Author: Chanson Parengkuan