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Crystals
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Rare-Earth Metal Compounds
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Rare-Earth Metal Compounds

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (31 July 2019) | Viewed by 20708

Special Issue Editor

Prof. Dr. Thomas Schleid

E-Mail Website
Guest Editor
Institute for Inorganic Chemistry, University of Stuttgart, 70569 Stuttgart, Germany
Interests: rare-earth metal compounds with mixed anions; luminescent materials; compounds with lone-pair oxoanions; hydroborates; thermoanalysis and phase and structure elucidation via X-ray diffraction
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Special Issue Information

Dear Colleagues,

The group of rare-earth metals covers 14+3 elements that range in atomic number from 58 (cerium) to 71 (lutetium) on the high end of the periodic table and are officially referred to as the 14 lanthanoids, since they all very much resemble their numerical forerunner lanthanum. From this point of view, these represent the horizontal 4f appendix of the vertical group 3, leading from scandium (no. 21) via yttrium (no. 39) to lanthanum (no. 57). Traditionally, rare-earth elements can be divided into two subgroups, based on their atomic weight: the light ones (lanthanum through gadolinium) and the heavy ones (terbium through lutetium), with a small grey area around europium (no. 63) and gadolinium (no. 64). Although light, yttrium is included in the group of the heavy rare-earth elements, typically occurring in the same geological deposits, because of its similar chemical properties and affinities. Just scandium, the smallest and lightest one, does not show extended relationships to all of them, except for their common trivalent oxidation state. Owing to the unusual physical and chemical properties of rare-earth metals and their compounds, they have been applied to many, diverse aspects of modern life and culture. Specific rare-earth elements are used individually or combined with others to generate phosphors in light-emitting devices, but still the glass industry is the largest consumer of raw materials containing rare-earth elements, using them for polishing and as additives providing color or special optical properties. Lanthanum- or cerium-based catalysts can be used to refine petroleum or in automotive exhaust–gas converters. Permanent magnets that employ special rare-earth metals are rapidly growing in application, since neodymium–iron–boron compounds represent the strongest of them. The use of lanthanum–nickel alloys as hydrogen-storage materials and as anodes in hydride batteries could help to initiate the triumphal procession of electrically-driven vehicles. For the removal of impurities in steel and the production of special alloys, the combination of lanthanum, cerium, praseodymium, and neodymium, commonly known as mischmetal, is unrivalled. In order to understand these exploitable properties, a sound knowledge of the underlying crystal structures is indispensable, so this Special Issue of Crystals might provide a first glance at new materials for the future.

Prof. Dr. Thomas Schleid
Guest Editor

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Keywords

  • Crystal Structure
  • Synthesis
  • Luminescence
  • Magnetism
  • Optical Properties

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Published Papers (5 papers)

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Research

13 pages, 3885 KiB  
Article
The Structural Dimorphism of Lanthanum Oxide Fluoride Selenide La2OF2Se
by Constantin Buyer, Hagen Grossholz and Thomas Schleid
Crystals 2019, 9(9), 435; https://doi.org/10.3390/cryst9090435 - 21 Aug 2019
Cited by 6 | Viewed by 4384
Abstract
The new colorless lanthanum oxide fluoride selenide La2OF2Se could be synthesized via solid-state reactions in two different structure types. Lamellar crystals of A-La2OF2Se were obtained from mixtures of La, LaF3, La2O [...] Read more.
The new colorless lanthanum oxide fluoride selenide La2OF2Se could be synthesized via solid-state reactions in two different structure types. Lamellar crystals of A-La2OF2Se were obtained from mixtures of La, LaF3, La2O3 and Se in molar ratios of 2:2:1:3 with NaCl as flux for seven days in silica-protected sealed tantalum capsules at 850 °C. Needle-shaped crystals of B‑La2OF2Se emerged from reactions of the same educt mixtures in molar ratios of 6:4:4:9 scheduled to produce La6O4F4Se3 with CsI as flux for four days in niobium ampoules at 700 °C. The A‑type form of La2OF2Se crystallizes in the trigonal space group R 3 ¯ m with a = 418.13(3) and c = 4478.2(4) pm for Z = 6, whereas the B‑type form is hexagonal (space group: P63/m) with a = 1396.82(9) and c = 401.08(3) pm for Z = 6. The crystal structure of A-La2OF2Se shows a close relationship to the fluoride-free La2O2Se and the oxygen-free La2F4Se. It can even be discussed as 1:1 intergrowth variety, since it contains the [LaO4Se3]11− and [LaF7Se3]10− polyhedra typical for the ternaries. B-La2OF2Se appears to be structurally very similar to La6O2F8Se3 in displaying [LaO3FSe4]12− and [LaOF6Se2]9− polyhedra. With 6.039 versus 6.036 g/cm3 the B-type form of La2OF2Se is slightly denser than the A-type variant. Full article
(This article belongs to the Special Issue Rare-Earth Metal Compounds)
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12 pages, 4017 KiB  
Article
Press to Success: Gd5FW3O16—The First Gadolinium(III) Fluoride Oxidotungstate(VI)
by Katharina V. Dorn and Ingo Hartenbach
Crystals 2019, 9(8), 424; https://doi.org/10.3390/cryst9080424 - 16 Aug 2019
Cited by 1 | Viewed by 4163
Abstract
The gadolinium(III) fluoride oxidotungstate(VI), with the formula Gd5FW3O16, represents the first published fluoride-derivative of a rare-earth metal oxidotungstate. It is synthesized by a mixture of GdF3, Gd2O3, and WO3 at [...] Read more.
The gadolinium(III) fluoride oxidotungstate(VI), with the formula Gd5FW3O16, represents the first published fluoride-derivative of a rare-earth metal oxidotungstate. It is synthesized by a mixture of GdF3, Gd2O3, and WO3 at 800 °C and a pressure of 2 GPa with the help of a belt press. The title compound crystallizes in the monoclinic space group P21/c (no. 14) with four formula units per unit cell and the following lattice parameters: a = 539.29 (4), b = 1556.41 (12), c = 1522.66 (11) pm, and β = 93.452 (4). The crystal structure comprises five crystallographically distinguishable Gd3+ cations, which are surrounded by either oxide and fluoride anions (Gd1–3) or by oxide anions only (Gd4, Gd5), with coordination numbers ranging between seven and nine. The fluoride anions are trigonal non-planar coordinated by three Gd3+ cations (Gd1–3). The distorted [WO6]6− octahedra in this structure form isolates edge- and vertex-connected entities of the compositions [W2O10]8− and [W2O11]10−, respectively. According to the presented units, a structured formula can be written as Gd4[FGd3]2[W2O10][W2O11]2. The single-crystal Raman spectrum reveals the typical symmetric stretching vibration mode of octahedral oxidotungstate(VI) units at about 871 cm−1. Full article
(This article belongs to the Special Issue Rare-Earth Metal Compounds)
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16 pages, 3209 KiB  
Article
Growth from the Melt and Properties Investigation of ScF3 Single Crystals
by Denis Karimov, Irina Buchinskaya, Natalia Arkharova, Pavel Prosekov, Vadim Grebenev, Nikolay Sorokin, Tatiana Glushkova and Pavel Popov
Crystals 2019, 9(7), 371; https://doi.org/10.3390/cryst9070371 - 20 Jul 2019
Cited by 12 | Viewed by 5334
Abstract
ScF3 optical quality bulk crystals of the ReO3 structure type (space group P m 3 ¯ m , a = 4.01401(3) Å) have been grown from the melt by Bridgman technique, in fluorinating atmosphere for the first time. Aiming to substantially [...] Read more.
ScF3 optical quality bulk crystals of the ReO3 structure type (space group P m 3 ¯ m , a = 4.01401(3) Å) have been grown from the melt by Bridgman technique, in fluorinating atmosphere for the first time. Aiming to substantially reduce vaporization losses during the growth process graphite crucibles were designed. The crystal quality, optical, mechanical, thermal and electrophysical properties were studied. Novel ScF3 crystals refer to the low-refractive-index (nD = 1.400(1)) optical materials with high transparency in the visible and IR spectral region up to 8.7 µm. The Vickers hardness of ScF3 (HV ~ 2.6 GPa) is substantially higher than that of CaF2 and LaF3 crystals. ScF3 crystals possess unique high thermal conductivity (k = 9.6 Wm−1К−1 at 300 K) and low ionic conductivity (σ = 4 × 10−8 Scm−1 at 673 К) cause to the structural defects in the fluorine sublattice. Full article
(This article belongs to the Special Issue Rare-Earth Metal Compounds)
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10 pages, 5157 KiB  
Article
Controlled Two-Step Formation of Faceted Perovskite Rare-Earth Scandate Nanoparticles
by Ryan J. Paull, Tiffany Ly, Zachary R. Mansley, Kenneth R. Poeppelmeier and Laurence D. Marks
Crystals 2019, 9(4), 218; https://doi.org/10.3390/cryst9040218 - 23 Apr 2019
Cited by 8 | Viewed by 4091
Abstract
A general approach to the formation of well-faceted nanoparticles is discussed and successfully applied to the production of several rare-earth scandates. Two steps were used, with higher temperatures first to nucleate the perovskite phase, followed by lower temperatures to smooth the particle surfaces. [...] Read more.
A general approach to the formation of well-faceted nanoparticles is discussed and successfully applied to the production of several rare-earth scandates. Two steps were used, with higher temperatures first to nucleate the perovskite phase, followed by lower temperatures to smooth the particle surfaces. Exploiting these two different regimes led to smaller nanoparticles with more faceting. This general approach may be tailored to other material systems as a step towards producing shape-controlled nanoparticles for a desired application. Full article
(This article belongs to the Special Issue Rare-Earth Metal Compounds)
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5 pages, 2030 KiB  
Communication
Y3Ru2−x—A Representative of a Composite Modulated Family of Intermetallics
by Sven Lidin and Laura Folkers
Crystals 2019, 9(4), 189; https://doi.org/10.3390/cryst9040189 - 1 Apr 2019
Cited by 2 | Viewed by 2130
Abstract
The compound Y3Ru2−x was synthesized from the elements and the structure was solved from single crystal synchrotron data. The high quality of the data allowed the determination of the incommensurate ordering of the compound, previously reported as disordered, with respect [...] Read more.
The compound Y3Ru2−x was synthesized from the elements and the structure was solved from single crystal synchrotron data. The high quality of the data allowed the determination of the incommensurate ordering of the compound, previously reported as disordered, with respect to the second subsystem. The compound crystallizes in the super space group X-3(00γ)0 with the q-vector axial along c*, q = 00γ, λ = 0.4276(7) and the centering vectors (1/3 2/3 0 1/3), (2/3 1/3 0 2/3). Full article
(This article belongs to the Special Issue Rare-Earth Metal Compounds)
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