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Crystals
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Functional Materials Based on Rare-Earth Elements
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Functional Materials Based on Rare-Earth Elements

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

Deadline for manuscript submissions: closed (31 May 2021) | Viewed by 19069

Special Issue Editors

Dr. Nataliya E. Novikova

E-Mail Website
Guest Editor
Federal Scientific Research Centre “Crystallography and Photonics,” Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russia
Interests: X-ray diffraction analysis, single crystals, structure–property relationship, phase transitions, nonlinear optical properties, structure of complex oxides
Dr. Irina I. Buchinskaya

E-Mail Website
Guest Editor
Shubnikov Institute of Crystallography of Federal Scientific Research Centre 'Crystallography and Photonics' of Russian Academy of Sciences, Leninskii Prospekt 59, 119333 Moscow, Russia
Interests: inorganic fluorides; phase diagrams; crystal growth; nonstoichiometry; rare earth ions; nanocrystalline materials; crystal characterization

Special Issue Information

Dear Colleagues,

Materials based on rare earth elements (REE) attract a lot of attention from researchers all around the world, without the use of which the creation and operation of many high-tech devices would be unthinkable. Due to their unique physicochemical characteristics, REE-based compounds have found wide application in the chemical industry, energy, laser technology, medicine, metallurgy, optics, and electronics. The spheres and possibilities of using REEs continue to actively expand; therefore, a comprehensive study of materials containing these metals seems to be a very urgent and important task. The study of the structural reasons for physical properties of promising crystalline materials not only expands the fundamental knowledge about them but also allows outlining the ways of creating new materials with controlled properties. The important distinctive properties of REEs include large ionic radii, the ability of most of them to change the oxidation state, and the tendency to form complex polyhedra with a high coordination number. The chemical similarity of REEs in the series distinguishes them from other metals in the periodic table of elements, where the chemical properties of two neighboring elements usually differ significantly. This makes it possible to “fine-tune” the properties of functional materials by changing the type and amount of rare earth elements in the composition of compounds.

We invite researchers to contribute to the Special Issue of “Functional Materials Based on Rare Earth Elements”, which aims to cover the broad aspects of studying the features of families of functional crystalline compounds based on rare earth elements with various cationic and anionic compositions.

The potential topics include but are not limited to:
- Synthesis and growth
- Structure solution
- Real structure and properties
- Theoretical aspects and computer modeling
- Exploitation of the remarkable properties in various applications

Dr. Nataliya E. Novikova
Dr. Irina I. Buchinskaya
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Rare earth ions
  • Inorganic materials
  • Nonstoichiometry
  • Crystal growth
  • Structure analysis
  • Structure–property relationship
  • Functional materials

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Published Papers (7 papers)

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Research

20 pages, 49421 KiB  
Article
Bridgman Growth and Physical Properties Anisotropy of CeF3 Single Crystals
by Denis N. Karimov, Dmitry S. Lisovenko, Anna G. Ivanova, Vadim V. Grebenev, Pavel A. Popov and Natalya L. Sizova
Crystals 2021, 11(7), 793; https://doi.org/10.3390/cryst11070793 - 7 Jul 2021
Cited by 12 | Viewed by 3326
Abstract
Bulk c-oriented CeF3 single crystals (sp. gr. P3¯c1) were grown successfully by the vertical Bridgman technique in a fluorinating atmosphere. A description of the crystal growth procedure and the solution of the difficulties during the growth [...] Read more.
Bulk c-oriented CeF3 single crystals (sp. gr. P3¯c1) were grown successfully by the vertical Bridgman technique in a fluorinating atmosphere. A description of the crystal growth procedure and the solution of the difficulties during the growth process are presented in detail. The anisotropy of the mechanical, thermal and electrophysical properties were studied for the first time. The maximum values of the thermal conductivity coefficient (α = 2.51 ± 0.12 W·m−1·K−1) and the ionic conductivity (σdc = 2.7 × 10−6 S/cm) at room temperature are observed in the [0001] direction for the CeF3 crystals. The Vickers (HV) and Berkovich (HB) microhardnesses for the (0001), (101¯0) and (112¯0) crystallographic planes were investigated. The HB values were higher than the HV ones and decreased from 3.8 to 2.9 GPa with an increase in the load in the range of 0.5–0.98 N for the hardest (0001) plane. The {112¯0}, {101¯0} and {0001} cleavage planes were observed during the indentation process of the CeF3 crystals. The variability of Young’s, the shear modules and Poisson’s ratio were analyzed. A significant correlation between the shapes of the Vickers indentation patterns with Young’s modulus anisotropy was found. The relationship between the anisotropy of the studied properties and the features of the CeF3 trigonal crystal structure is discussed. Full article
(This article belongs to the Special Issue Functional Materials Based on Rare-Earth Elements)
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9 pages, 2574 KiB  
Article
Refinement of the Congruently Melting Composition of Nonstoichiometric Fluorite Crystals Ca1-xYxF2x (x = 0.01–0.14)
by Denis N. Karimov, Elena A. Sulyanova and Boris P. Sobolev
Crystals 2021, 11(6), 696; https://doi.org/10.3390/cryst11060696 - 17 Jun 2021
Cited by 1 | Viewed by 1855
Abstract
The concentration series of nonstoichiometric crystals Ca1–xYxF2+x (x = 0.01–0.14) was obtained from a melt by directional crystallization to refine the composition of the temperature maximum on the melting curves. A precision (±9 × [...] Read more.
The concentration series of nonstoichiometric crystals Ca1–xYxF2+x (x = 0.01–0.14) was obtained from a melt by directional crystallization to refine the composition of the temperature maximum on the melting curves. A precision (±9 × 10−5 Å) determination of lattice parameters of the Ca1–xYxF2+x crystals with the structure of fluorite (sp. gr. Fm-3m) was performed, and a linear equation of their concentration dependence was calculated: a(x) = 5.46385(5) + 0.1999(4) x. The distribution of yttrium along the crystals Ca1–xYxF2+x, the content of which is determined by the precision lattice parameters, is studied. The congruently melting composition x = 0.105(5) of the Ca1–xYxF2+x phase is refined by the method of directional crystallization. Full article
(This article belongs to the Special Issue Functional Materials Based on Rare-Earth Elements)
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11 pages, 2323 KiB  
Article
La1–yBayF3–y Solid Solution Crystals as an Effective Solid Electrolyte: Growth and Properties
by Irina I. Buchinskaya, Denis N. Karimov and Nikolay I. Sorokin
Crystals 2021, 11(6), 629; https://doi.org/10.3390/cryst11060629 - 31 May 2021
Cited by 15 | Viewed by 2297
Abstract
A series of nonstoichiometric La1–yBayF3–y (0 ≤ y ≤ 0.12) single crystals with a tysonite-type structure (sp. gr. P-3c1) was grown from the melt by the directional crystallization method in a fluorinating atmosphere, [...] Read more.
A series of nonstoichiometric La1–yBayF3–y (0 ≤ y ≤ 0.12) single crystals with a tysonite-type structure (sp. gr. P-3c1) was grown from the melt by the directional crystallization method in a fluorinating atmosphere, and some physical properties were characterized. The concentration dependence of electrical conductivity σdc(y) La1–yBayF3–y crystals was studied. The composition of the ionic conductivity maximum for this solid electrolyte was refined. It was confirmed that the maximum conductivity σmax = 8.5 × 10–5 S/cm (295 K) was observed at the composition ymax = 0.05 ± 0.01. Analysis of the electrophysical data for the group of tysonite-type solid electrolytes R1–yMyF3–y (M = Ca, Sr, Ba, Eu2+ and R = La, Ce, Pr, Nd) showed that the compositions of the maxima of their conductivity were close and amount to y = 0.03−0.05. This fact indicates a weak influence of the size effect (ionic radii R3+ and M2+) on the value of ymax for R1–yMyF3–y solid electrolytes. Full article
(This article belongs to the Special Issue Functional Materials Based on Rare-Earth Elements)
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12 pages, 3916 KiB  
Article
Structure and Properties of Ln2MoO6 Oxymolybdates (Ln = La, Pr, Nd) Doped with Magnesium
by Ekaterina Orlova, Elena Kharitonova, Timofei Sorokin, Alexander Antipin, Nataliya Novikova, Nataliya Sorokina and Valentina Voronkova
Crystals 2021, 11(6), 611; https://doi.org/10.3390/cryst11060611 - 28 May 2021
Cited by 4 | Viewed by 2519
Abstract
The literature data and the results obtained by the authors on the study of the structure and properties of a series of polycrystalline and single-crystal samples of pure and Mg-doped oxymolybdates Ln2MoO6 (Ln = La, Pr, Nd) are analyzed. [...] Read more.
The literature data and the results obtained by the authors on the study of the structure and properties of a series of polycrystalline and single-crystal samples of pure and Mg-doped oxymolybdates Ln2MoO6 (Ln = La, Pr, Nd) are analyzed. Presumably, the high-temperature phase I41/acd of Nd2MoO6 single crystals is retained at room temperature. The reason for the loss of the center of symmetry in the structures of La2MoO6 and Pr2MoO6 and the transition to the space group I4¯c2 is the displacement of oxygen atoms along the twofold diagonal axes. In all structures, Mg cations are localized near the positions of the Mo atoms, and the splitting of the positions of the atoms of rare-earth elements is found. Thermogravimetric studies, as well as infrared spectroscopy data for hydrated samples of Ln2MoO6 (Ln = La, Pr, Nd), pure and with an impurity of Mg, confirm their hygroscopic properties. Full article
(This article belongs to the Special Issue Functional Materials Based on Rare-Earth Elements)
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9 pages, 1523 KiB  
Article
Displacements in the Cationic Motif of Nonstoichiometric Fluorite Phases Ba1−xRxF2+x as a Result of the Formation of {Ba8[R6F68–69]} Clusters: III. Defect Cluster Structure of the Nonstoichiometric Phase Ba0.69La0.31F2.31 and Its Dependence on Heat Treatment
by Elena A. Sulyanova, Denis N. Karimov and Boris P. Sobolev
Crystals 2021, 11(4), 447; https://doi.org/10.3390/cryst11040447 - 20 Apr 2021
Cited by 8 | Viewed by 2051
Abstract
The defect structure of Ba0.69La0.31F2.31 single crystals in as-grown state and after annealing at 1173 K for 336 h was studied by X-ray diffraction analysis. Both crystals belong to the CaF2 structure type (sp. gr. [...] Read more.
The defect structure of Ba0.69La0.31F2.31 single crystals in as-grown state and after annealing at 1173 K for 336 h was studied by X-ray diffraction analysis. Both crystals belong to the CaF2 structure type (sp. gr. Fm3¯m). They have vacancies in the main anion motif and interstitial fluorine anions in Wyckoff positions 48i and 4b. Relaxation (static displacement of some main anions to Wyckoff position 32f) is observed in the annealed crystal. It was established that annealing leads to a change in the type of displacement of the main anions in Wyckoff positions 8c from dynamic to static. Displacement of La3+ cations to Wyckoff position 32f is observed in both crystals. A model of the defect structure of Ba0.69La0.31F2.31 is proposed, according to which interstitial fluorine anions and La3+ cations are aggregated into [Ba14−nLanF64+n] clusters with the cuboctahedral anionic core formed by interstitial fluorine anions in Wyckoff positions 48i. Ba2+ cations are located in the cluster in the centers of the faces, and the La3+ cations are shifted by 0.24 Å from the vertices of the cluster along the three-fold axis towards the center of the cluster. The study establishes the relationship between the defect structure of crystals and their structurally sensitive properties, and to develop approaches to their management. Full article
(This article belongs to the Special Issue Functional Materials Based on Rare-Earth Elements)
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17 pages, 5813 KiB  
Article
Growth Peculiarities and Properties of KR3F10 (R = Y, Tb) Single Crystals
by Denis N. Karimov, Irina I. Buchinskaya, Natalia A. Arkharova, Anna G. Ivanova, Alexander G. Savelyev, Nikolay I. Sorokin and Pavel A. Popov
Crystals 2021, 11(3), 285; https://doi.org/10.3390/cryst11030285 - 14 Mar 2021
Cited by 19 | Viewed by 3531
Abstract
Cubic KR3F10 (R = Y, Tb) single crystals have been successfully grown using the Bridgman technique. Growth of crystals of this type is complicated due to the hygroscopicity of potassium fluoride and melt overheating. The solution to the [...] Read more.
Cubic KR3F10 (R = Y, Tb) single crystals have been successfully grown using the Bridgman technique. Growth of crystals of this type is complicated due to the hygroscopicity of potassium fluoride and melt overheating. The solution to the problem of oxygen-incorporated impurities has been demonstrated through the utilization of potassium hydrofluoride as a precursor. In this study, the crystal quality, structure features, and optical, thermal and electrophysical properties of KR3F10 were examined. Data on the temperature dependences of conductivity properties of KTb3F10 crystals were obtained for the first time. These crystals indicated thermal conductivity equal to 1.54 ± 0.05 Wm−1K−1 at room temperature caused by strong phonon scattering in the Tb-based crystal lattice. Ionic conductivities of KY3F10 and KTb3F10 single crystals were 4.9 × 10−8 and 1.2 × 10−10 S/cm at 500 K, respectively, and the observed difference was determined by the activation enthalpy of F− ion migration. Comparison of the physical properties of the grown KR3F10 crystals with the closest crystalline analog from the family of Na0.5−xR0.5+xF2+2x (R = Tb, Y) cubic solid solutions is reported. Full article
(This article belongs to the Special Issue Functional Materials Based on Rare-Earth Elements)
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13 pages, 16998 KiB  
Article
Upconversion Nanoparticles Encapsulated with Amorphous Silica and Their Emission Quenching by FRET: A Nanosensor Excited by NIR for Mercury Detection
by Wei Wu, Wei Wei, Dingli Xu, Yunpeng Liu, Jin Li, Kaifeng Gan and Liang Liu
Crystals 2021, 11(2), 104; https://doi.org/10.3390/cryst11020104 - 25 Jan 2021
Cited by 1 | Viewed by 2334
Abstract
Near-infrared (NIR) region has been considered as a diagnostic window since it avoids sample autofluorescence and light scattering. Upconversion nanoparticles (UCNPs) convert NIR light into high energy excitation light, making them a suitable excitation source for nanoprobes with deep penetration depth and high [...] Read more.
Near-infrared (NIR) region has been considered as a diagnostic window since it avoids sample autofluorescence and light scattering. Upconversion nanoparticles (UCNPs) convert NIR light into high energy excitation light, making them a suitable excitation source for nanoprobes with deep penetration depth and high signal-to-noise ratio. The current work reported a rhodamine-derived probe for the detection of Hg(II). Corresponding absorption and emission responses for Hg(II) and detailed recognizing mechanism were discussed. An absorption titration experiment was performed. It was found that Hg(II) directly bonded with probe with chemical stoichiometry of 1:1, its association constant was calculated as 2.59 × 105 M−1. Such a high value indicated a direct coordination affinity between Hg(II) and this rhodamine-derived probe. Most metal cations exerted no increasing effect on the probe emission or absorption, exhibiting good sensing selectivity of probe towards Hg(II). Upconversion nanoparticles (UCNPs) were firstly encapsulated with silica (SiO2) and then bonded with the probe via a covalent bond. Given a near-infrared (NIR) laser excitation with wavelength of 980 nm, this probe, (E)-2-((3′,6′-bis(diethylamino)-2′,7′-dimethyl-3-oxospiro[isoindoline-1,9′-xanthen]-2-yl)imino)acetaldehyde (denoted as RHO), captured the energy of UCNPs via a FRET (fluorescence resonance energy transfer) path, resulting in the emission quenching of UCNPs. This composite system showed linear sensing behavior towards Hg(II) with high selectivity, which was similar to the case of pure probe. No probe emission, however, was observed from the composite system, which was different from the case of most literature reports. The self-quenching between probe molecules was claimed responsible for the probe emission, which was confirmed by experiment result and analysis. To the best of our knowledge, this is the first demonstration of covalently integrating SiO2-coated UCNPs with a rhodamine-derived probe for Hg(II) sensing. Full article
(This article belongs to the Special Issue Functional Materials Based on Rare-Earth Elements)
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