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

Deadline for manuscript submissions: closed (31 August 2023) | Viewed by 15432

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Prof. Dr. Maria Milanova

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Faculty of Chemistry and Pharmacy, Sofia University, Sofia, Bulgaria
Interests: inorganic chemistry; material science; chemistry of rare earths; photocatalysis; environmental problems
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Dr. Martin Tsvetkov

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Department of Inorganic Chemistry, Faculty of Chemistry and Pharmacy, University of Sofia “St. Kliment Ohridsky”, Sofia, Bulgaria
Interests: solid-state chemistry; material characterization; crystallography; heterogeneous catalysis and photocatalysis
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Special Issue Information

Dear Colleagues,

The articles included in the first volume of the Special Issue, “Rare Earths-Doped Materials”, published in Crystals 2020, 10; Crystals 2021, 11; and Crystals 2022, 12, as well as our personal experience, make it clear that the interest and research on the subject is continuing intensively. Therefore, with this letter, we announce the second volume of Rare Earths-Doped Materials and invite you to participate. The focus of the Issue is on the research and investigation of RE-doped materials: the methods for their synthesis and characterization, as well as the development of new properties (optical, magnetic, photocatalytic, biological, etc.). Topics of interest for the Special Issue include: (i) the development and application of different methods to obtain RE-doped materials; (ii) the application of different techniques for material characterization; (iii) RE-doped materials with specific structural and optical properties.

We encourage the submission of high-quality manuscripts in the form of research articles, short communications, and reviews for contribution to the second release of this Special Issue.

Prof. Dr. Maria Milanova
Dr. Martin Tsvetkov
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 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

rare earth elements
single crystals
bulk crystals
nanocrystals
phosphors
composite materials
semiconductors
insulators

Related Special Issues

Rare Earths-Doped Materials in Crystals (9 articles)
Rare Earths-Doped Materials (3rd Edition) in Crystals (2 articles)

Published Papers (11 papers)

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Research

23 pages, 3154 KiB

Open AccessArticle

Influence of Synthesis Conditions on the Crystal, Local Atomic, Electronic Structure, and Catalytic Properties of (Pr_1−xYb_x)₂Zr₂O₇ (0 ≤ x ≤ 1) Powders

by Victor V. Popov, Ekaterina B. Markova, Yan V. Zubavichus, Alexey P. Menushenkov, Alexey A. Yastrebtsev, Bulat R. Gaynanov, Olga V. Chernysheva, Andrei A. Ivanov, Sergey G. Rudakov, Maria M. Berdnikova, Alexander A. Pisarev, Elizaveta S. Kulikova, Nickolay A. Kolyshkin, Evgeny V. Khramov, Victor N. Khrustalev, Igor V. Shchetinin, Nadezhda A. Tsarenko, Natalia V. Ognevskaya and Olga N. Seregina

Crystals 2023, 13(9), 1405; https://doi.org/10.3390/cryst13091405 - 21 Sep 2023

Cited by 1 | Viewed by 2666

Abstract

The influence of Yb³⁺ cations substitution for Pr³⁺ on the structure and catalytic activity of (Pr_1−xYb_x)₂Zr₂O₇ powders synthesized via coprecipitation followed by calcination is studied using a combination of long- (s-XRD), medium- (Raman, FT-IR, and SEM-EDS) and short-range (XAFS) sensitive methods, as well as adsorption and catalytic techniques. It is established that chemical composition and calcination temperature are the two major factors that govern the phase composition, crystallographic, and local-structure parameters of these polycrystalline materials. The crystallographic and local-structure parameters of (Pr_1−xYb_x)₂Zr₂O₇ samples prepared at 1400 °C/3 h demonstrate a tight correlation with their catalytic activity towards propane cracking. The progressive replacement of Pr³⁺ with Yb³⁺ cations gives rise to an increase in the catalytic activity. A mechanism of the catalytic cracking of propane is proposed, which considers the geometrical match between the metal–oxygen (Pr–O, Yb–O, and Zr–O) bond lengths within the active sites and the size of adsorbed propane molecule to be the decisive factor governing the reaction route. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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12 pages, 3389 KiB

Open AccessArticle

Highly Efficient Orange-Red Emission in Sm³⁺-Doped Yttrium Gallium Garnet Single Crystal

by Huiting Zhang, Zhonghua Zhu, Shengdi Ta, Ninghan Zeng, Limin Wu, Wenxia Wu, Peng Zhang, Shoulei Xu, Bernard Albert Goodman and Wen Deng

Crystals 2023, 13(8), 1273; https://doi.org/10.3390/cryst13081273 - 18 Aug 2023

Cited by 3 | Viewed by 915

Abstract

High-quality single crystals with empirical composition Y₂.₉₆Sm₀.₀₄Ga₅O₁₂ (YGG: Sm³⁺) were successfully prepared by the optical floating zone method for the first time and compared with related single crystals of Y₂.₉₆Sm₀.₀₄Al₅O₁₂ (YAG: Sm³⁺). With both crystals, XRD showed that Sm³⁺ entered the cubic-phase structure. Optical absorption spectra produced a series of peaks from Sm³⁺ in the 250 nm to 550 nm range, and photoluminescence excitation (PLE) spectra detected at 613 nm showed strong excitation peaks at 407 nm and 468 nm. A strong emission peak at 611 nm (orange-red light) was observed in the photoluminescence (PL) spectra under excitations at both 407 and 468 nm, respectively, but it was much brighter under excitation at 407 nm. Furthermore, with both emission spectra, the peaks from the YGG: Sm³⁺ crystal were significantly more intense than those from the YAG: Sm³⁺ crystal, and both experienced a blue shift. In addition, under excitation at 407 nm, the color purity of the emitted orange-red light of YGG: Sm³⁺ was higher than that of the YAG: Sm³⁺ crystal, and the fluorescence lifetime for the ⁴G_5/2 → ⁶H_7/2 transition of YGG: Sm³⁺ was longer than that of the YAG: Sm³⁺ crystal. The optical properties of the YGG: Sm³⁺ crystal are better than those of the YAG: Sm³⁺ crystal. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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10 pages, 1351 KiB

Open AccessArticle

Influence of Golden Nanoparticles on the Incorporation of Eu²⁺ into BaI₂ and Defect Concentration

by Katarína Ridzoňová, Maksym Buryi, Vladimir Babin, David John, Jan Drahokoupil, Neda Neykova, Tatsiana Salamakha and Yauhen Tratsiak

Crystals 2023, 13(6), 902; https://doi.org/10.3390/cryst13060902 - 01 Jun 2023

Viewed by 870

Abstract

Conjugated BaI₂:Eu (5 at.%) nanocrystalline particles were synthesized, decorated with golden nanoparticles (GNP). GNP demonstrated some hydrophilic effect, leading to the BaI₂·H₂O phase creation. The Eu²⁺ luminescence intensity was reduced according to the GNP content. This was due to the decreased number of Eu²⁺ ions in the BaI₂, most probably, arising from the Au substitution for Ba competing with Eu. Moreover, the decay time of luminescence was decreased upon GNP content. This was explained by the moderation of negative charge in the GNP, leading to the repulsion with an electron in the excited Eu²⁺. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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16 pages, 4227 KiB

Open AccessArticle

Mechanochemically Synthesized Solid Solutions La_1−xCe_xFeO_3+x/2 for Activation of Peroxydisulfate in Catalytical Reaction for Tetracycline Degradation

by Martin Tsvetkov, Elzhana Encheva, Stefani Petrova, Ivanka Spassova and Maria Milanova

Crystals 2023, 13(5), 769; https://doi.org/10.3390/cryst13050769 - 05 May 2023

Cited by 2 | Viewed by 1058

Abstract

The synthesis of orthoferrites of the type La_1−xCe_xFeO_3+x/2, x = 0.00, 0.01, 0.03, 0.05, and 0.07, by applying a simple and effective mechanochemical transformation from the constituent oxides is presented. Physicochemical methods such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Vis spectroscopy, and Brunauer–Emmett–Teller (BET) adsorption were applied to gain information about the effect of Ce⁴⁺ content on the structural, textural, and optical properties of the samples. The catalytic activity of the samples for water decontamination was determined in a photo-Fenton-like activation of persulfate for removal of tetracycline hydrochloride as model pollutant. The presence of persulfate, PDS, considerably increased the removal efficiency under visible light illumination. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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14 pages, 5165 KiB

Open AccessArticle

The Role of Er³⁺ Content in the Luminescence Properties of Y₃Al₅O₁₂ Single Crystals: Incorporation into the Lattice and Defect State Creation

by Maksym Buryi, Amayès Médhi Gaston-Bellegarde, Jan Pejchal, Fedor Levchenko, Zdeněk Remeš, Katarína Ridzoňová, Vladimir Babin and Sergii Chertopalov

Crystals 2023, 13(4), 562; https://doi.org/10.3390/cryst13040562 - 25 Mar 2023

Cited by 2 | Viewed by 1019

Abstract

Erbium-doped Y₃Al₅O₁₂ (YAG) single crystals grown using the micro-pulling-down technique were investigated. Three Er concentrations were chosen: 0.1, 0.3 and 1 at%. Er³⁺ electron paramagnetic resonance (EPR) spectra were measured in the ground and first excited states. The corresponding g tensors and ¹⁶⁷Er hyperfine interaction were changing upon Er content indicating moderation of the Er-O bond length and/or Er local surrounding. Photoluminescence (PL) and radioluminescence (RL) spectra were complex, consisting of strongly overlapped typical Er³⁺ transitions. In addition, there were other broad PL band (3.1 eV) and RL band (3.95 eV) attributed to the F⁺ center and yttrium substituting for aluminum (Y_Al), respectively. The X-ray excited decay kinetics exhibited a decrease of the decay time of the Y_Al from hundreds of nanoseconds to nanoseconds upon Er doping level. This is discussed and explained considering EPR data. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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13 pages, 6613 KiB

Open AccessArticle

Impact of Erbium Doping in the Structural and Magnetic Properties of the Anisotropic and Frustrated SrYb₂O₄ Antiferromagnet

by Diana Lucia Quintero-Castro, Juanita Hincapie, Abhijit Bhat Kademane, Minki Jeong, Matthias Frontzek, Alexandra Franz, Amutha Ramachandran, Fabiano Yokaichiya, J Ross Stewart and Rasmus Toft-Petersen

Crystals 2023, 13(3), 529; https://doi.org/10.3390/cryst13030529 - 20 Mar 2023

Viewed by 1480

Abstract

We present a systematic study of the structural and magnetic properties of a series of powder samples of SrYb

_{2 - x}

_{x}

_{4}

with different Yb/Er concentrations. Magnetometry and neutron diffraction have been used to study the magnetic ground states [...] Read more.

We present a systematic study of the structural and magnetic properties of a series of powder samples of SrYb

_{2 - x}

_{x}

_{4}

with different Yb/Er concentrations. Magnetometry and neutron diffraction have been used to study the magnetic ground states of the compound series, while inelastic neutron scattering was used to investigate the crystal field excitations for a chosen concentration. These results show that the crystal structure remains the same for all compositions, while the lattice parameters increase linearly with the Er content. All compounds showed some type of magnetic transition below 1 K, however, both the magnetic structure and nature of the phase transition vary throughout the series. The samples present a non-collinear magnetic structure with the moments lying on the ab plane for low Er content. For high Er content, the magnetic structure is collinear with the moments aligned along the c-axis. A critical concentration is found where there is a bifurcation between zero-field and field-cooled magnetic susceptibility. This irreversible process could be due to the random mixture of single-ion magnetic anisotropies. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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12 pages, 4391 KiB

Open AccessArticle

Up-Conversion Photoluminescence in Thulia and Ytterbia Co-Doped Yttria-Stabilized Zirconia Single Crystals

by Danni Huang, Tong Xiao, Beibei Fu, Shoulei Xu, Yuyang Huang, Wen Deng and Zhukun Zhou

Crystals 2023, 13(3), 460; https://doi.org/10.3390/cryst13030460 - 07 Mar 2023

Cited by 2 | Viewed by 1220

Abstract

ZrO₂ is an attractive host matrix for luminescence material because of its excellent physical properties, such as low phonon energy and wide band gap. In this work, the highly transparent Tm₂O₃ and Yb₂O₃ co-doped yttria stabilized zirconia (YSZ) (abbreviated as Yb/Tm: YSZ) single crystals were grown by the optical floating zone method. The Yb/Tm: YSZ samples were stabilized in the cubic phase at room temperature when Yb³⁺ and Tm³⁺ replaced Y³⁺. The influence of Yb³⁺ co-doping on the up-conversion luminescence properties of the crystals was systematically studied. A total of 0.5 mol% Tm₂O₃ and 2.0 mol% Yb₂O₃ co-activated YSZ single crystal (abbreviated as 2.0Yb/Tm: YSZ) has the maximum luminous intensity. There were seven absorption peaks located at around 358, 460, 679, 783.3, 850–1000, 1200, and 1721.5 nm that were observed in the absorption spectrum of the 2.0Yb/Tm: YSZ single crystal. There were three up-conversion peaks at around 488, 658 and 800 nm that were observed when the Yb/Tm: YSZ samples were excitated at 980 nm. The fluorescence lifetime of Tm³⁺ for the ¹G₄→³H₆ transition of the 2.0Yb/Tm: YSZ sample is 7.716 ms as excited with a 980 nm laser. In addition, the oscillator strength parameters Ω_λ (λ = 2, 4 and 6) of this sample were derived by the Judd–Ofelt theory to evaluate the laser performance of the host materials. The ratio Ω₄/Ω₆ of this sample is 0.80, implying its excellent laser output. Therefore, the 2.0Yb/Tm: YSZ single crystal is a considerable potential material for laser and luminescence applications. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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15 pages, 4658 KiB

Open AccessArticle

Structural and Spectroscopic Effects of Li⁺ Substitution for Na⁺ in Li_xNa_1−xCaLa_0.5Er_0.05Yb_0.45(MoO₄)₃ Upconversion Scheelite-Type Phosphors

by Chang Sung Lim, Aleksandr Aleksandrovsky, Maxim Molokeev, Aleksandr Oreshonkov and Victor Atuchin

Crystals 2023, 13(2), 362; https://doi.org/10.3390/cryst13020362 - 20 Feb 2023

Cited by 8 | Viewed by 1290

Abstract

New triple molybdates Li_xNa_1−xCaLa_0.5(MoO₄)₃:Er³⁺0.05/Yb³⁺0.45 (x = 0, 0.05, 0.1, 0.2, 0.3) were manufactured successfully using the microwave-assisted sol-gel-based technique (MAS). Their room-temperature crystal structures were determined in space group I4₁/a by Rietveld analysis. The compounds were found to have a scheelite-type structure. In Li-substituted samples, the sites of big cations were occupied by a mixture of (Li, Na, La, Er, Yb) ions, which provided a linear cell volume decrease with the Li content increase. The increased upconversion (UC) efficiency and Raman spectroscopic properties of the phosphors were discussed in detail. The mechanism of optimization of upconversion luminescence upon Li content variation was shown to be due to the control of excitation/energy transfer channel, while the control of luminescence channels played a minor role. The UC luminescence maximized at lithium content x = 0.05. The mechanism of UC optimization was shown to be due to the control of excitation/energy transfer channel, while the control of luminescence channels played a minor role. Over the whole spectral range, the Raman spectra of Li_xNa_1−xCaLa_0.5(MoO₄)₃ doped with Er³⁺ and Yb³⁺ ions were totally superimposed with the luminescence signal of Er³⁺ ions, and increasing the Li⁺ content resulted in the difference of Er³⁺ multiple intensity. The density functional theory calculations with the account for the structural disorder in the system of Li, Na, Ca, La, Er and Yb ions revealed the bandgap variation from 3.99 to 4.137 eV due to the changing of Li content. It was found that the direct electronic transition energy was close to the indirect one for all compounds. The determined chromaticity points (ICP) of the LiNaCaLa(MoO₄)₃:Er³⁺,Yb³⁺ phosphors were in good relation to the equal-energy point in the standard CIE (Commission Internationale de L’Eclairage) coordinates. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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15 pages, 3451 KiB

Open AccessArticle

Ultrathin Rare-Earth-Doped MoS₂ Crystalline Films Prepared with Magnetron Sputtering and Ar + H₂ Post-Annealing

by Chenglin Heng, Xuan Wang, Chaonan Zhao, Gang Wu, Yanhui Lv, Hanchun Wu, Ming Zhao and Terje G. Finstad

Crystals 2023, 13(2), 308; https://doi.org/10.3390/cryst13020308 - 13 Feb 2023

Cited by 1 | Viewed by 1509

Abstract

In this work, we propose a method to prepare large-area, crystalline ultrathin rare-earth (RE, i.e., Eu, Yb, Er and Tb)-doped MoS₂ thin films, using magnetron sputtering and subsequent Ar + H₂ annealing. The film thickness of as-deposited samples varied from 60 to 100 nm, and decreases to be below 10 nm after annealing at 550 °C for 30 min. X-ray diffraction and Raman spectra analysis revealed that the sample films were crystallized after the annealing, which resulted in a MoS₂ crystallite size of about 4–5 nm. X-ray photoelectron spectroscopy indicated that most of the RE ions existed in the films in trivalent states. The optical bandgap of the RE-doped MoS₂ samples decreased from 1.6 eV (undoped) to 1.3 eV (Eu-doped) in the UV-vis absorption spectra. Electrical measurements showed that the electrical resistance decreased from 9.13 MΩ (undoped) to 0.34 MΩ (Yb-doped), the carrier density increased by one to two orders of magnitude and the carrier mobility decreased from 5.4 cm²/V·s (undoped) to 0.65 cm²/V·s (Yb-doped). The sign of the Hall coefficients indicated that the undoped MoS₂ and the Yb-, Tb- and Er-doped MoS₂ samples were n-type semiconductors, while the Eu-doped sample showed p-type characteristics. This study may be helpful to broaden the photoelectronic applications of these two-dimensional materials. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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15 pages, 10501 KiB

Open AccessArticle

The Effect of Ne⁺ Ion Implantation on the Crystal, Magnetic, and Domain Structures of Yttrium Iron Garnet Films

by Igor Fodchuk, Andrij Kotsyubynsky, Andrii Velychkovych, Ivan Hutsuliak, Volodymyra Boychuk, Volodymyr Kotsyubynsky and Liubomyr Ropyak

Crystals 2022, 12(10), 1485; https://doi.org/10.3390/cryst12101485 - 19 Oct 2022

Cited by 1 | Viewed by 1482

Abstract

The mechanism of the influence of crystal inhomogeneities on the magnetic and domain microstructures of functional materials based on yttrium iron garnet heterostructures is an important subject of investigation due to the aim to predict parameters for manufacturingpurposes. A study of the structural and magnetic characteristics of a set of yttrium iron garnet films grown on gadolinium–gallium garnet substrate is presented. High-resolution X-ray diffractometry, Mössbauer spectroscopy, MFM, as well as ion implantation simulation and X-ray diffraction simulation were used together to determine the features of the effect of Ne⁺ ion implantation with different dose rates on the samples. The simulation of ion implantation with E = 82 keV showed energy loss profiles of Ne ions with subsequent defect formation up to amorphization of near-surface layers at high doses. Implantation creates two magnetically non-equivalent types of tetrahedrally located Fe³⁺ ions, which leads to a rotation of the total magnetic moment relative to the film surface and a change in the width of the magnetic domain stripes. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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8 pages, 3397 KiB

Open AccessArticle

Synthesis and Upconversion Luminescence Properties of BaBiO₂Cl:Yb³⁺,Er³⁺ Phosphor

by Zhuanzhuan Zhang and Yanjie Liang

Crystals 2022, 12(10), 1465; https://doi.org/10.3390/cryst12101465 - 17 Oct 2022

Cited by 1 | Viewed by 1221

Abstract

The interaction of near-infrared (NIR) light with matter that produces high-energy visible light emissions is known as photon upconversion, which has shown promising applications in different fields, including optoelectronics, biomedicine and photovoltaics. In this paper, a novel BaBiO₂Cl:Yb³⁺,Er³⁺ upconversion phosphor was successfully synthesized through a simple high-temperature solid-state reaction route. The crystal structure, phase purity, microstructure and upconversion luminescence properties of the as-prepared phosphor were characterized comprehensively. The XRD and SEM results clearly demonstrate the successful synthesis of the target phosphors with high purity. When excited by a 980 nm NIR laser, the as-prepared BaBiO₂Cl:Yb³⁺,Er³⁺ phosphor exhibited intense red upconversion luminescence due to the Er³⁺ ⁴F_9/2→⁴I_15/2 transition, which enabled this phosphor to have high promise for important applications, such as anti-counterfeiting and advanced photonics. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

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