Recent Developments of Crystallography in RAS (Russian Academy of Sciences)

A special issue of Crystals (ISSN 2073-4352).

Deadline for manuscript submissions: closed (30 June 2023) | Viewed by 20214

Special Issue Editor


E-Mail Website
Guest Editor
Shubnikov Institute of Crystallography of Federal Scientific Research Centre “Crystallography and Photonics”, Russian Academy of Sciences, Moscow, Russia
Interests: solution crystal growth; physics of crystallization; X-ray diffraction topography; mechanisms of defects formation; space materials science

Special Issue Information

Dear Colleagues,

Modern crystallography involves the study of crystals’ growth, structure, and properties, focusing on their mutual connection and mutual influence. This methodology is also effective for the study of complex crystal systems, such as crystalline composites, nanostructures, and ordered hierarchical structures. The purpose of the broad scientific discussion on these problems is to develop an understanding of the mechanisms of crystal formation, crystal structure defects, phase formation and phase interaction in multiphase systems, as well as their influence on the structure and properties of materials and the search for ways to control the properties of materials on this basis. As a result, research on the structure and properties of crystalline materials in connection with the conditions used for their preparation is necessary.

Although all of the above issues relate to the field of fundamental knowledge, the most accurate relationships between the method used for obtaining the composition, structure, and properties of materials are often revealed in the course of applied research when the conditions used for obtaining the material are selected carefully in order to achieve the best results in terms of structure and properties. Therefore, we also welcome applied work aimed at creating materials with desired properties. We do not put any restrictions on the type of materials obtained. We are interested in inorganic, organic, and hybrid crystalline materials and composites; partially ordered and disordered systems; supramolecular assemblies, etc.

Among the most pressing problems, the following should be highlighted:

- the structure of crystals and complex crystal systems;

- the structural conditionality of the properties of materials;

- the processes of formation of crystalline materials and systems;

- the mechanisms and kinetics of phase transitions;

- the mechanisms of defect formation in multicomponent and multiphase systems;

- crystalline nanocomposites and the relationship between their composition, structure, and properties, as well as the interaction of crystalline particles with the matrix;

- supramolecular systems.

Dr. Alexey Voloshin
Guest Editor

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 2600 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

  • crystal growth
  • optical properties of crystals
  • electric properties of crystals
  • magnetic properties of crystals
  • multicomponent and multiphase systems
  • defect formation
  • phase transitions
  • nanomaterials
  • composite materials
  • hierarchical structure
  • supramolecular systems

Published Papers (16 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Research

14 pages, 2251 KiB  
Article
Impact of Schwoebel Barriers on the Step-Flow Growth of a Multicomponent Crystal
by Alexey Redkov
Crystals 2024, 14(1), 25; https://doi.org/10.3390/cryst14010025 - 26 Dec 2023
Viewed by 762
Abstract
The step-flow and spiral growth of a multicomponent crystal are considered from vapors, taking into account the different possible Schwoebel barriers for each component within the Burton-Cabrera-Frank model. Analytic expressions for the final growth rates of such a multicomponent crystal are determined while [...] Read more.
The step-flow and spiral growth of a multicomponent crystal are considered from vapors, taking into account the different possible Schwoebel barriers for each component within the Burton-Cabrera-Frank model. Analytic expressions for the final growth rates of such a multicomponent crystal are determined while considering the kinetic properties of all the individual components and growth conditions. Possible instabilities inherent in the presence of several components are studied, and a stability criterion for the multicomponent case is proposed. It is shown that, in certain cases, nucleation of nanoislands of pure components behind the moving steps can initiate, significantly distorting the growth process. The criterion for the occurrence of such an unstable regime is found. Full article
Show Figures

Figure 1

20 pages, 10299 KiB  
Article
Crystals of 4,7-Di-2-thienyl-2,1,3-benzothiadiazole and Its Derivative with Terminal Trimethylsilyl Substituents: Synthesis, Growth, Structure, and Optical-Fluorescent Properties
by Valery A. Postnikov, Georgy A. Yurasik, Artem A. Kulishov, Timofei A. Sorokin, Maria S. Lyasnikova, Nataliya I. Sorokina, Maxim S. Skorotetcky, Vlada V. Popova, Lev L. Levkov, Oleg V. Borshchev, Evgeniya A. Svidchenko, Nikolay M. Surin and Sergey A. Ponomarenko
Crystals 2023, 13(12), 1697; https://doi.org/10.3390/cryst13121697 - 18 Dec 2023
Viewed by 998
Abstract
Among short donor–acceptor molecules with a central benzothiadiazole fragment, 4,7-di-2-thienyl-2,1,3-benzothiadiazole (T-BTD) is one of the most well-known compounds, valued for its photophysical and semiconductor properties. We have synthesized a derivative of 4,7-di-2-thienyl-2,1,3-benzothiadiazole with trimethylsilyl end-substituents, 4,7-bis(5-(trimethylsilyl)thiophen-2-yl)benzothiadiazole (TMS-T-BTD). The phase transition parameters and thermal [...] Read more.
Among short donor–acceptor molecules with a central benzothiadiazole fragment, 4,7-di-2-thienyl-2,1,3-benzothiadiazole (T-BTD) is one of the most well-known compounds, valued for its photophysical and semiconductor properties. We have synthesized a derivative of 4,7-di-2-thienyl-2,1,3-benzothiadiazole with trimethylsilyl end-substituents, 4,7-bis(5-(trimethylsilyl)thiophen-2-yl)benzothiadiazole (TMS-T-BTD). The phase transition parameters and thermal stability of T-BTD and TMS-T-BTD were investigated using DSC and TGA methods. The presence of the trimethylsilyl end-groups in TMS-T-BTD significantly enhances solubility, increases the melting temperature, and improves the resistance of TMS-T-BTD to evaporation in the liquid state. Single crystals of T-BTD and TMS-T-BTD were grown from solutions, with the largest sizes being 7 × 2 × 0.5 mm3 and 8 × 1 × 0.45 mm3, respectively. Using single-crystal X-ray diffraction at 293 K, the crystal structure of T-BTD was refined in the rhombic system (sp.gr. Pcab, Z = 8), while for TMS-T-BTD, it was determined for the first time in the monoclinic system (sp.gr. P21/c, Z = 4). The relationship between observed growth anisotropy and molecular packing in the crystals was analyzed. The results of investigations into the spectral-fluorescent properties of solutions in hexane and THF are presented. The solvatochromic effect was studied in a series of solvents, including hexane, THF, dichloromethane, and acetonitrile. The photostability of the compounds in hexane solutions was examined. It was found that the quantum yield of photodestruction for T-BTD is 13 times higher than that of TMS-T-BTD. The fluorescent properties of T-BTD and TMS-T-BTD crystals were investigated. Full article
Show Figures

Figure 1

15 pages, 6166 KiB  
Article
Implementation of Phase Transitions in Rb3H(SO4)2 under K Substitution
by Ivan S. Timakov, Vladimir A. Komornikov, Elena V. Selezneva and Vadim V. Grebenev
Crystals 2023, 13(9), 1401; https://doi.org/10.3390/cryst13091401 - 21 Sep 2023
Viewed by 655
Abstract
A series of solid acid compounds, representing the large family MmHn(AO4)(m + n)/2·yH2O (where M = K, Rb, Cs, NH4; AO4 = SO4, SeO4, [...] Read more.
A series of solid acid compounds, representing the large family MmHn(AO4)(m + n)/2·yH2O (where M = K, Rb, Cs, NH4; AO4 = SO4, SeO4, HPO4, HAsO4), is characterized by high values of own proton conductivity, which arises as a result of a phase transition through the formation of a dynamically disordered hydrogen bond network. Such superprotonic phase transitions are observed, however, not for all compounds of the family and Rb3H(SO4)2 is one of them. The occurrence of superprotonic phase transitions has been experimentally demonstrated in the (KxRb1−x)3H(SO4)2 solid solutions through cation substitution. The high-temperature phases are unstable towards decomposition reaction, and their temperature range of existence is about 1–7 °C. The implementation of superprotonic transitions is discussed in terms of hydrogen bond lengths. Full article
Show Figures

Figure 1

11 pages, 2322 KiB  
Article
Growth and Structure of Rare-Earth Molybdate Crystals Na0.65La4.35Mo3O15.81±δF0.07±ε
by Nataliya E. Novikova, Ekaterina I. Orlova, Alexander M. Antipin, Timofei A. Sorokin, Vladimir B. Kvartalov, Elena P. Kharitonova, Nataliya I. Sorokina, Olga A. Alekseeva and Valentina I. Voronkova
Crystals 2023, 13(9), 1293; https://doi.org/10.3390/cryst13091293 - 22 Aug 2023
Viewed by 670
Abstract
Rare-earth sodium- and fluorine-substituted molybdates with the Na0.65La4.35Mo3O15.81±δF0.07±ε composition were synthesized for the first time as single crystals. An accurate X-ray diffraction analysis of three samples at room temperature showed that the obtained crystals [...] Read more.
Rare-earth sodium- and fluorine-substituted molybdates with the Na0.65La4.35Mo3O15.81±δF0.07±ε composition were synthesized for the first time as single crystals. An accurate X-ray diffraction analysis of three samples at room temperature showed that the obtained crystals are isostructural to undoped cubic compounds of the Ln5Mo3O16+δ family (space group Pn3¯n). Sodium cations partially occupy one of the two lanthanum positions and center the more distorted LaO8 polyhedra, while fluorine anions occupy over-stoichiometric oxygen positions in the vast interstices (cavities) of the structure. The partial substitution of fluorine atoms for oxygen ones affects the transport characteristics of compounds by activating the oxygen atoms in the anionic subsystem due to the effect of supplementary electrostatic repulsion between anions of different types. Full article
Show Figures

Figure 1

12 pages, 2053 KiB  
Article
Features of Phase Formation in the CsOH–H2SO4–H3PO4–H2O System and the Growth of the Cs6(SO4)3(H3PO4)4 Crystals
by V. A. Komornikov, I. P. Makarova, I. S. Timakov and V. V. Grebenev
Crystals 2023, 13(8), 1163; https://doi.org/10.3390/cryst13081163 - 26 Jul 2023
Viewed by 672
Abstract
In this paper, the conditions of phase formation in the system CsOH–H2SO4–H3PO4–H2O are considered for the first time. The phase formation of Cs6(SO4)3(H3PO4) [...] Read more.
In this paper, the conditions of phase formation in the system CsOH–H2SO4–H3PO4–H2O are considered for the first time. The phase formation of Cs6(SO4)3(H3PO4)4 at t = 50 °C has been studied extensively. The main concentration boundary conditions for this compound are considered for the first time. The solubility congruence of Cs6(SO4)3(H3PO4)4 is shown. Conditions and approaches for obtaining crystals by isothermal evaporation and saturated solution temperature reduction methods are considered. The results of obtaining Cs6(SO4)3(H3PO4)4 crystals with maximum dimensions of ~20 mm are presented. Full article
Show Figures

Figure 1

20 pages, 8119 KiB  
Article
Crystal Structure of Bismuth-Containing Samarium Iron–Aluminium Borates Sm1−xBixFe3−yAly(BO3)4 (x = 0.05–0.07, y = 0–0.28) in the Temperature Range of 25–500 K
by Ekaterina S. Smirnova, Olga A. Alekseeva, Vladimir V. Artemov, Timofei A. Sorokin, Dmitry N. Khmelenin, Ekaterina V. Sidorova, Kirill V. Frolov and Irina A. Gudim
Crystals 2023, 13(7), 1128; https://doi.org/10.3390/cryst13071128 - 19 Jul 2023
Viewed by 821
Abstract
Structural features of new mixed bismuth-containing samarium iron–aluminium borate single crystals Sm1−xBixFe3−yAly(BO3)4 (x = 0.05–0.07, y = 0–0.28) were studied using X-ray diffraction analysis based on aluminium content and [...] Read more.
Structural features of new mixed bismuth-containing samarium iron–aluminium borate single crystals Sm1−xBixFe3−yAly(BO3)4 (x = 0.05–0.07, y = 0–0.28) were studied using X-ray diffraction analysis based on aluminium content and temperature in the range 25–500 K. The crystals were grown using the solution-in-melt technique with Bi2Mo3O12 in a flux. The composition of the single crystals was analyzed using energy-dispersive X-ray fluorescence and energy-dispersive X-ray elemental analysis. Temperature dependencies of Sm1−xBixFe3−yAly(BO3)4 unit-cell parameters were studied. Negative thermal expansion was identified below 100 K and represented by characteristic surfaces of the thermal expansion tensor. (Sm,Bi)–O, (Sm,Bi)–(Fe,Al), (Fe,Al)–(Fe,Al), and (Fe,Al)–O interatomic distances decreased with the addition of aluminium atoms. An increase in the (Fe,Al)–(Fe,Al) intrachain bond length at low temperatures in the magnetically ordered state weakened this bond, whereas a decrease in the (Fe,Al)–(Fe,Al) interchain distance strengthened super-exchange paths between different chains. It was found that the addition of aluminium atoms influenced interatomic distances in Sm1−xBixFe3−yAly(BO3)4 much more than lowering the temperature from 293 K to 25 K. The effect of aluminium doping on magnetoelectric properties and structural symmetry of rare-earth iron borates is also discussed. Full article
Show Figures

Figure 1

15 pages, 6071 KiB  
Article
One-Dimensional NaSn2F5 Crystals Inside Single-Walled Carbon Nanotubes
by Ruslan M. Zakalyukin, Ekaterina A. Levkevich and Andrey S. Kumskov
Crystals 2023, 13(7), 1065; https://doi.org/10.3390/cryst13071065 - 6 Jul 2023
Viewed by 1042
Abstract
Crystals of NaSn2F5 were obtained from an aqueous solution. Their morphology and habitus were studied via scanning electron microscopy and X-ray phase diffraction analysis. The crystals obtained have a long prismatic shape with a very large aspect ratio (>100). The [...] Read more.
Crystals of NaSn2F5 were obtained from an aqueous solution. Their morphology and habitus were studied via scanning electron microscopy and X-ray phase diffraction analysis. The crystals obtained have a long prismatic shape with a very large aspect ratio (>100). The faceting of the crystal is represented by the (110) face, while the (100) face is practically absent. A nanocomposite incorporating one-dimensional (1D) NaSn2F5@SWCNT crystals was synthesized from the melt by means of the capillary wetting technique. The embedded fragment is represented by two planes of Sn cations, which provide contrast in high-resolution electron microscopy images. The cation plane is represented by the (110) crystallographic plane of the NaSn2F5 structure. The crystallographic direction [22¯3] coincides with the nanotube axis. The first layer of Sn cations forms a hexagonal network with Sn atoms at its nodes. The tin atoms in the second layer are arranged according to the closest spherical packing law in a plane, but with a distance between atoms that is two times greater than that in the first layer. Sn cations’ hexagon sizes are ~0.87 nm and ~0.69 nm in size. According to the Raman spectroscopy data, the nanocomposite behaves as an electron acceptor. The SWCNT diameter of 1.54 nm revealed using NaSn2F5@SWCNT Raman spectroscopy corresponds to their diameter in electron microscope images and the diameter used for modeling. Full article
Show Figures

Figure 1

9 pages, 3131 KiB  
Article
Rare-Earth Fluorite-like Li0.42La4.58Mo3O15.76±δF0.42±ε Molybdates: Crystal Growth and Atomic Structure
by Ekaterina I. Orlova, Timofei A. Sorokin, Vladimir B. Kvartalov, Alexander M. Antipin, Nataliya E. Novikova, Elena P. Kharitonova, Nataliya I. Sorokina, Olga A. Alekseeva and Valentina I. Voronkova
Crystals 2023, 13(7), 1009; https://doi.org/10.3390/cryst13071009 - 25 Jun 2023
Cited by 3 | Viewed by 775
Abstract
Rare-earth fluorine-containing molybdates of the Ln5Mo3O16+δ oxygen–electron conductor family with the LiLa4Mo3O15F composition were synthesized for the first time as single crystals by the flux method. An accurate X-ray diffraction analysis of [...] Read more.
Rare-earth fluorine-containing molybdates of the Ln5Mo3O16+δ oxygen–electron conductor family with the LiLa4Mo3O15F composition were synthesized for the first time as single crystals by the flux method. An accurate X-ray diffraction analysis of the obtained crystals was carried out at 20 and −183 °C. The LiLa4Mo3O15F compound is isostructural to the fluorine-free analogue with a cubic structure (space group Pn3¯n). It is shown that lithium atoms replace one of the two positions of lanthanum in the more distorted LaO8 polyhedron. According to X-ray diffraction analysis, fluorine atoms replace the positions of over-stoichiometric oxygen located in the vast cavities of the structure. So, fluorine anions can promote the interstitial conductivity of F-containing LiLa4Mo3O15F molybdates. Full article
Show Figures

Figure 1

19 pages, 9207 KiB  
Article
Growth and Characterization of Centimeter-Scale Pentacene Crystals for Optoelectronic Devices
by Valery A. Postnikov, Artem A. Kulishov, Georgy A. Yurasik, Nataliya I. Sorokina, Timofei A. Sorokin and Vadim V. Grebenev
Crystals 2023, 13(7), 999; https://doi.org/10.3390/cryst13070999 - 22 Jun 2023
Viewed by 1247
Abstract
In this work, we present results on the growth of centimeter-scale pentacene crystals using the physical vapor transport method in a dual-temperature zone horizontal furnace. It was established that intensive crystal growth processes occurred in transition regions with sudden temperature changes, while crystal [...] Read more.
In this work, we present results on the growth of centimeter-scale pentacene crystals using the physical vapor transport method in a dual-temperature zone horizontal furnace. It was established that intensive crystal growth processes occurred in transition regions with sudden temperature changes, while crystal growth was practically not observed in regions with slightly varying temperatures. During crystal growth, co-precipitating golden needle-like crystals reaching lengths of more than 10 mm were obtained. Using the method of single-crystal X-ray diffraction at 85 and 293 K for dark-blue lamellar pentacene crystals, the crystal structure was refined in a triclinic system with sp.gr. P1¯. It was established that the golden needle crystals consisted of molecules of the pentacene derivative—5,14-pentacenedione, the crystal structure of which was solved for the first time in a rhombic system with sp.gr. P212121. The absorption and luminescence spectra of pentacene and 5,14-pentacenedione in toluene solutions were obtained and analyzed. The electrical properties of the prepared pentacene thin films and single crystals grown under physical vapor transport conditions were evaluated by fabricating and characterizing field-effect transistors (FETs). It was shown that the presence of impurities in the commercial pentacene material had a significant effect on the morphological quality of thin polycrystalline films and noticeably reduced the hole mobility. Full article
Show Figures

Figure 1

15 pages, 19600 KiB  
Article
Structural Peculiarities of Natural Ballas—Spheroidal Variety of Polycrystalline Diamond
by Andrei A. Shiryaev, Felix V. Kaminsky, Anton D. Pavlushin, Vasily O. Yapaskurt, Denis A. Zolotov, Alexei A. Averin, Olga M. Zhilicheva, Maximilian S. Nickolsky and Olga V. Kuznetsova
Crystals 2023, 13(4), 624; https://doi.org/10.3390/cryst13040624 - 5 Apr 2023
Viewed by 1465
Abstract
Ballas is a rare polycrystalline diamond variety characterized by a radially oriented internal structure and spheroidal outer shape. The origin of natural ballases remains poorly constrained. We present the results of a comprehensive investigation of two classic ballas diamonds from Brazil. External morphology [...] Read more.
Ballas is a rare polycrystalline diamond variety characterized by a radially oriented internal structure and spheroidal outer shape. The origin of natural ballases remains poorly constrained. We present the results of a comprehensive investigation of two classic ballas diamonds from Brazil. External morphology was studied using SEM, high-resolution 3D optical microscopy, and X-ray tomography. Point and extended defects were examined on polished central plates using infra-red, photo- and cathodoluminescence spectroscopies, and electron back-scattering diffraction; information about nanosized inclusions was inferred from Transmission Electron Microscopy. The results suggest that fibrous diamond crystallites comprising ballas are split with pronounced rotation, causing concentric zoning of the samples. Pervasive feather-like luminescing structural features envelop single crystalline domains and most likely represent fibers with non-crystallographic branching. These features are enriched in N3 point defects. Twinning is not common. The nitrogen content of the studied samples reaches 700 at.ppm; its concentration gradually increases from the center to the rim. Annealing of the ballases took place at relatively high temperatures of 1125–1250 °C; the annealing continued even when the samples were fully grown, as suggested by the presence of the H4 nitrogen-related defects in the outer rim. Presumably, the ballas diamond variety was formed at high supersaturation but in conditions favoring a small growth kinetic coefficient. The carbon isotopic composition of the studied ballases (δ13C = −5.42, −7.11‰) belongs to the main mode of mantle-derived diamonds. Full article
Show Figures

Figure 1

13 pages, 2878 KiB  
Article
Spiral Pitch Control in Cholesteric Liquid Crystal Layers with Hybrid Boundary Conditions
by Serguei P. Palto, Dmitry O. Rybakov, Boris A. Umanskii and Nikolay M. Shtykov
Crystals 2023, 13(1), 10; https://doi.org/10.3390/cryst13010010 - 21 Dec 2022
Cited by 1 | Viewed by 1561
Abstract
The optical spectra of the cholesteric liquid crystal (CLC) layers under conditions of hybrid anchoring show a short-wave shift under a pulsed electric field. This behavior is anomalous because it is associated with a decrease in the pitch of the cholesteric spiral, which [...] Read more.
The optical spectra of the cholesteric liquid crystal (CLC) layers under conditions of hybrid anchoring show a short-wave shift under a pulsed electric field. This behavior is anomalous because it is associated with a decrease in the pitch of the cholesteric spiral, which is atypical at conditions when the electric field is perpendicular to the axis of the CLC spiral. An analytical model of the phenomenon is discussed, according to which the spiral pitch under hybrid boundary conditions can be greater than the natural pitch in an unlimited volume of CLC. An in-plane electric field, being localized near the homeotropic-alignment surface, can be treated as effectively influencing the azimuthal anchoring and leading to a variety of metastable states with both increased and decreased pitch. These metastable states with local minima of free energy prevent the spiral from unwinding, and corresponding bands of selective reflection can even be shifted to the short-wave region of the spectrum. The observed effect is also studied numerically. It is shown by numerical simulations that the localized electric field from short-pitch electrodes can also modify zenithal anchoring, which should allow for defect-free controlling of the spiral pitch and spectral stop-band location. Full article
Show Figures

Figure 1

15 pages, 2803 KiB  
Article
VOLDIS: A Direct Search for the Size Distribution of Nanoparticles from Small-Angle Scattering Data and Stability of the Solution
by Vladimir V. Volkov
Crystals 2022, 12(11), 1659; https://doi.org/10.3390/cryst12111659 - 18 Nov 2022
Cited by 2 | Viewed by 1320
Abstract
The paper considers an algorithm for the direct search for a nonparametric smooth histogram of the particle size distribution from small-angle X-ray and neutron scattering data. The features and details of the implementation of the method, which consists in the sequential search for [...] Read more.
The paper considers an algorithm for the direct search for a nonparametric smooth histogram of the particle size distribution from small-angle X-ray and neutron scattering data. The features and details of the implementation of the method, which consists in the sequential search for several solutions with different degrees of smoothness of the distribution contour, are considered. Methods for evaluating the stability of both the whole distribution contour and its individual parts are discussed. The work of the program is illustrated by examples of the analysis of polydisperse spherical particles in silicasol solutions. Full article
Show Figures

Figure 1

14 pages, 2624 KiB  
Article
Heat-Mediated Transformation of PMMA-SiO2 Core-Shell Particles into Hollow SiO2 Particles
by Nadezhda S. Sukhinina, Vladimir M. Masalov, Tatiana N. Fursova, Igor I. Khodos, Irina I. Zverkova, Andrey A. Zhokhov and Gennadi A. Emelchenko
Crystals 2022, 12(7), 883; https://doi.org/10.3390/cryst12070883 - 21 Jun 2022
Cited by 2 | Viewed by 1902
Abstract
Changes in the morphology and structure of the core-shell particles of polymethyl methacrylate-silicon dioxide and hollow SiO2 particles during their heat treatment were studied by electron microscopy, infrared spectroscopy, and X-ray diffraction. The polymeric core of the PMMA-SiO2 hybrid particle was [...] Read more.
Changes in the morphology and structure of the core-shell particles of polymethyl methacrylate-silicon dioxide and hollow SiO2 particles during their heat treatment were studied by electron microscopy, infrared spectroscopy, and X-ray diffraction. The polymeric core of the PMMA-SiO2 hybrid particle was found to undergo an unusual transformation when exposed to the electron microscope beam: its shrinkage occurs through the formation of a spherical cavity. It was shown that the process of silica-shell formation occurs in the temperature range of 200–600 °C and is accompanied by the loss of vinyl- and OH-groups. It was determined by the method of X-ray diffraction, that in the place of the interaction of PMMA and the shell, the degree of ordering of the polymer is higher than that in the volume of the polymer core. It was shown that the frequency of the TO3-vibrational mode (asymmetric stretching vibrations of the Si–O–Si bonds) increases with an increase in the annealing temperature, which is associated with the densification of the silicon dioxide shell. Full article
Show Figures

Figure 1

12 pages, 4150 KiB  
Article
The High-Energy Milling Preparation and Spectroscopic Characterization of Rare-Earth Ions Doped BaY2F8 Nanoparticles
by Aleksander V. Koshelev, Natalia A. Arkharova, Kirill V. Khaydukov, Mir Saeed Seyed Dorraji, Denis N. Karimov and Vera V. Klechkovskaya
Crystals 2022, 12(5), 599; https://doi.org/10.3390/cryst12050599 - 24 Apr 2022
Viewed by 2002
Abstract
BaY2F8 nanoparticles (NPs), doped with Yb3+ and Er3+ ions, were successfully produced by high-energy ball-milling. High-quality monoclinic single crystals (sp. gr. C2/m, a = 0.6969(3), b = 1.0502(1), c = 0.4254(1) nm, β [...] Read more.
BaY2F8 nanoparticles (NPs), doped with Yb3+ and Er3+ ions, were successfully produced by high-energy ball-milling. High-quality monoclinic single crystals (sp. gr. C2/m, a = 0.6969(3), b = 1.0502(1), c = 0.4254(1) nm, β = 99.676°) grown from the melt by the Bridgman technique were used as raw materials. The prepared nanocrystals were comprehensively studied by X-ray diffraction analysis, transmission electron microscopy, and optical spectroscopy. The fabrication possibility of single-phase irregular shaped Ba(Y0.964Yb0.030Er0.006)2F8 NPs in the size range of 20–100 nm with a milling duration of 10 h at 600 rpm is demonstrated. Ba(Y0.964Yb0.030Er0.006)2F8 NPs show intense luminescence by both up- (λ = 540 and 650 nm) and down-conversion (λ = 1540 nm) mechanisms upon IR excitation (λ = 980 nm). A qualitative comparison of the spectroscopic characteristics of the produced Ba(Y0.964Yb0.030Er0.006)2F8 NPs with the initial bulk crystal and the widely used up-conversion β-Na1.5(Y1.17Yb0.3Er0.03)F6 NPs is presented. Experimental data offer great opportunities of the Ba(Y0.964Yb0.030Er0.006)2F8 NPs applications in nanophotonics and biotechnology. High-energy ball-milling has potential as a versatile method for the scalable production of fluoride nanoparticles. Full article
Show Figures

Graphical abstract

13 pages, 2647 KiB  
Article
Influence of Growth Conditions on Mechanical Properties of K2NiXCo(1−X) (SO4)2·6H2O Crystals
by Natalia A. Vasilyeva, Elena B. Rudneva, Vera L. Manomenova, Marina V. Koldaeva and Alexey E. Voloshin
Crystals 2021, 11(12), 1550; https://doi.org/10.3390/cryst11121550 - 11 Dec 2021
Cited by 1 | Viewed by 1765
Abstract
K2NiXCo(1−X) (SO4)2·6H2O (KCNSH) mixed crystal is a promising material for solar blind optical filters, combining high transparency in the ultraviolet range with effective suppression of the visible spectral region. Increasing the mechanical [...] Read more.
K2NiXCo(1−X) (SO4)2·6H2O (KCNSH) mixed crystal is a promising material for solar blind optical filters, combining high transparency in the ultraviolet range with effective suppression of the visible spectral region. Increasing the mechanical strength of these crystals is important to enable them to be machined in the manufacture of optical elements. A comprehensive study of the inhomogeneities and crack resistance of KCNSH crystal as a function of the growth conditions was carried out. The influence of the radial and mosaic inhomogeneity, as well as other structural defects, on the crack resistance of the crystals was analyzed. To assess the crack resistance of crystals, the parameters ca (crack length), c/a (the ratio of crack length to the size of the indentation), and KC (fracture toughness) were used. The correctness of the obtained results was analyzed. The conditions for growing KCNSH crystals with the best crack resistance were determined on the basis of the results of the study. It is shown that growing the mixed crystals using the temperature difference technique with a peripheral solution supply into the shaper provides the best crystal quality. Full article
Show Figures

Figure 1

7 pages, 1291 KiB  
Article
The Influence of Supercooling and Hydrodynamics on the Mosaic and Radial Inhomogeneity of K2NiXCo(1–X)(SO4)2·6H2O Mixed Crystal
by Natalia A. Vasilyeva, Elena B. Rudneva, Vera L. Manomenova, Yuriy V. Grigoriev and Alexey E. Voloshin
Crystals 2021, 11(11), 1368; https://doi.org/10.3390/cryst11111368 - 10 Nov 2021
Cited by 2 | Viewed by 1124
Abstract
The mosaic and radial inhomogeneity of shaped mixed crystals of K2NixCo(1–x)(SO4)2·6H2O (KCNSH) were studied depending on the supercooling of solution, its velocity and its method of supply into the shaper. It [...] Read more.
The mosaic and radial inhomogeneity of shaped mixed crystals of K2NixCo(1–x)(SO4)2·6H2O (KCNSH) were studied depending on the supercooling of solution, its velocity and its method of supply into the shaper. It was shown that mosaic inhomogeneity could be suppressed when solution is supercooled to about 2 °C. Peripheral supply of the solution (tangential to the wall of the shaper to create a “swirling” flow) with a rate of 55–135 cm/s provides better composition uniformity along the crystal surface in comparison with upright supply of the solution (flow is perpendicular to the crystal surface). Full article
Show Figures

Figure 1

Back to TopTop