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Crystals
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Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals
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Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals

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

Deadline for manuscript submissions: closed (15 June 2022) | Viewed by 28975

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Alessandra Toncelli

E-Mail Website
Guest Editor
Department of Physics, University of Pisa, 56126 Pisa, PI, Italy
Interests: photonics; rare-earth luminescence; optical spectroscopy; THz spectroscopy; crystal growth
Special Issues, Collections and Topics in MDPI journals
Dr. Željka Antić

E-Mail Website
Guest Editor
Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, University of Belgrade, Belgrade, Serbia
Interests: luminescence; luminescence thermometry; phosphors; advanced optical materials; sensors
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Photonics applications based on rare-earth (RE) doped crystals are developing in many different fields, such as photovoltaic, laser technology, optical data storage, sensing, bioimaging, diagnosis, and therapy. RE-doped inorganic bulk materials are long been known to have luminescence emissions that are spectrally distributed throughout the whole optical range from the ultraviolet (UV) to the mid-infrared region with unique features which have made these materials very important especially for laser applications.  Moreover, when grown in nanometric size, these materials exhibit peculiar behaviours for their efficiency, lifetimes, energy transfer processes, interaction with the environment, etc., which have stimulated new research devoted, on the one hand, to the physical understanding of these phenomena and on the other hand, to the development of many new applications. This Special Issue is devoted both to the study of RE-doped bulk crystal and nanocrystal materials from a scientific point of view and to the presentation of their possible applications in any field.

We invite researchers to contribute to the Special Issue “Optical and Spectroscopic Properties of Rare-Earth Doped Crystals”, which is intended to serve as a unique multidisciplinary forum covering all aspects of science, technology, and applications of RE-doped crystals starting from the growth techniques with specific attention to the emission features of these materials and their applications.

Potential topics include, but are not limited to:

  • synthesis and growth of RE-doped crystals
  • new host materials for efficient emission
  • upconversion efficiency
  • characterisation of RE-doped crystals by spectroscopic, microscopic, and other advanced techniques
  • analysis of the energy transfer processes
  • biomedical and imaging applications
  • integrated optics applications
  • photovoltaic applications
  • sensing applications

Prof. Dr. Alessandra Toncelli
Dr. Željka Antić
Guest Editors

Manuscript Submission Information

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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.

Published Papers (13 papers)

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Research

12 pages, 3195 KiB  
Article
Saturation Spectroscopic Studies on Yb3+ and Er3+ Ions in Li6Y(BO3)3 Single Crystals
by Gábor Mandula, Zsolt Kis, Krisztián Lengyel, László Kovács and Éva Tichy-Rács
Crystals 2022, 12(8), 1151; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12081151 - 16 Aug 2022
Viewed by 1414
Abstract
The results of a series of pump–probe spectral hole-burning experiments are presented on Yb3+- or Er3+-doped Li6Y(BO3)3 (LYB) single crystals in the temperature range of 2–14 K and 9–28 K, respectively. The spectral hole [...] Read more.
The results of a series of pump–probe spectral hole-burning experiments are presented on Yb3+- or Er3+-doped Li6Y(BO3)3 (LYB) single crystals in the temperature range of 2–14 K and 9–28 K, respectively. The spectral hole has a complex structure for Yb3+ with superposed narrow and broad bands, while a single absorption hole has been observed for Er3+. Population relaxation times (T1) at about 850 ± 60 μs and 1010 ± 50 μs and dipole relaxation times (T2) with values of 1100 ± 120 ns and 14.2 ± 0.3 ns have been obtained for the two components measured for the Yb3+:2F7/2—2F5/2 transition. T1 = 402 ± 8 μs and T2 = 11.9 ± 0.2 ns values have been found for the Er3+:4I15/2—4I11/2 excitation. The spectral diffusion rate at about 1 and 5 MHz/ms has been determined for the narrow and broad spectral line in Yb3+-doped crystal, respectively. The temperature dependence of the spectral hole halfwidth has also been investigated. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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14 pages, 10198 KiB  
Article
Optical Properties of Yttria-Stabilized Zirconia Single-Crystals Doped with Terbium Oxide
by Yazhao Wang, Zhonghua Zhu, Shengdi Ta, Zeyu Cheng, Peng Zhang, Ninghan Zeng, Bernard Albert Goodman, Shoulei Xu and Wen Deng
Crystals 2022, 12(8), 1081; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12081081 - 01 Aug 2022
Cited by 4 | Viewed by 2110
Abstract
A series of yttria-stabilized zirconia single-crystals doped with 0.000–0.250 mol% Tb4O7 was prepared by the optical floating-zone method. As shown by XRD and Raman spectroscopy, all of the crystals had a cubic-phase structure. These were initially orange–yellow in color, which [...] Read more.
A series of yttria-stabilized zirconia single-crystals doped with 0.000–0.250 mol% Tb4O7 was prepared by the optical floating-zone method. As shown by XRD and Raman spectroscopy, all of the crystals had a cubic-phase structure. These were initially orange–yellow in color, which is indicative of the presence of Tb4+ ions, but they then became colorless after being annealed in a H2/Ar atmosphere as a result of the reduction of Tb4+ to Tb3+. The absorption spectra of the unannealed samples show both the 4f 8→4f 75d1 transition of Tb3+ ions and the Tb4+ charge-transfer band. In addition, the transmittance of the crystals was increased by annealing. Under irradiation with 300 nm of light, all of the single-crystal samples showed seven emission peaks in the visible region, corresponding to the decay from the 5D3,4 excited state of Tb3+ to the 7FJ (J = 6–0) states. The most intense emission was at 544 nm, which corresponds to the typical strong green emission from the 5D4→7F5 transition in Tb3+ ions. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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12 pages, 2295 KiB  
Article
Infrared Photoluminescence of Nd-Doped Sesquioxide and Fluoride Nanocrystals: A Comparative Study
by Fulvia Gennari, Milica Sekulić, Tanja Barudžija, Željka Antić, Miroslav D. Dramićanin and Alessandra Toncelli
Crystals 2022, 12(8), 1071; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12081071 - 31 Jul 2022
Cited by 2 | Viewed by 1404
Abstract
Lanthanide ions possess various emission channels in the near-infrared region that are well known in bulk crystals but are far less studied in samples with nanometric size. In this work, we present the infrared spectroscopic characterization of various Nd-doped fluoride and sesquioxide nanocrystals, [...] Read more.
Lanthanide ions possess various emission channels in the near-infrared region that are well known in bulk crystals but are far less studied in samples with nanometric size. In this work, we present the infrared spectroscopic characterization of various Nd-doped fluoride and sesquioxide nanocrystals, namely Nd:Y2O3, Nd:Lu2O3, Nd:Sc2O3, Nd:YF3, and Nd:LuF3. Emissions from the three main emission bands in the near-infrared region have been observed and the emission cross-sections have been calculated. Moreover, another decay channel at around 2 μm has been observed and ascribed to the 4F3/2→4I15/2 transition. The lifetime of the 4F3/2 level has been measured under LED pumping. Emission cross-sections for the various compounds are calculated in the 1 μm, 900 nm, and 1.3 μm regions and are of the order of 10−20 cm2 in agreement with the literature results. Those in the 2 μm region are of the order of 10−21 cm2. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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9 pages, 3866 KiB  
Article
Rapid Aqueous-Phase Synthesis and Photoluminescence Properties of K0.3Bi0.7F2.4:Ln3+ (Ln = Eu, Tb, Pr, Nd, Sm, Dy) Nanocrystalline Particles
by Weili Wang, Shihai Miao, Dongxun Chen and Yanjie Liang
Crystals 2022, 12(7), 963; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12070963 - 10 Jul 2022
Cited by 1 | Viewed by 1363
Abstract
Trivalent lanthanides (Ln3+) doped bismuth-based inorganic compounds have attracted considerable interest as promising candidates for next-generation inorganic luminescent materials. Here, a series of K0.3Bi0.7F2.4 (KBF) nanocrystalline particles with controlled morphology have been synthesized through a low-temperature [...] Read more.
Trivalent lanthanides (Ln3+) doped bismuth-based inorganic compounds have attracted considerable interest as promising candidates for next-generation inorganic luminescent materials. Here, a series of K0.3Bi0.7F2.4 (KBF) nanocrystalline particles with controlled morphology have been synthesized through a low-temperature aqueous-phase precipitation method. Using KBF as the host matrix, Eu3+, Tb3+, Pr3+, Nd3+, Sm3+, and Dy3+ ions are introduced to obtain K0.3Bi0.7F2.4:Ln3+ (KBF:Ln) nanophosphors. The as-prepared KBF:Ln nanophosphors exhibit commendable photoluminescence properties, in which multicolor emissions in a single host lattice can be obtained by doping different Ln3+ ions when excited by ultraviolet light. Moreover, the morphology and photoluminescence performance of these nanophosphors remain unchanged under different soaking times in water, showing good stability in a humid environment. The proposed simple and rapid synthesis route, low-cost and nontoxic bismuth-based host matrix, and tunable luminescent colors will lead the way to access these KBF:Ln nanophosphors for appealing applications such as white LEDs and optical thermometry. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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10 pages, 3743 KiB  
Article
Room Temperature Synthesis of Various Color Emission Rare-Earth Doped Strontium Tungstate Phosphors Applicable to Fingerprint Identification
by Soung-Soo Yi and Jae-Yong Jung
Crystals 2022, 12(7), 915; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12070915 - 27 Jun 2022
Cited by 3 | Viewed by 1447
Abstract
Crystalline SrWO4 was synthesized at room temperature using a co-precipitation method. To use the SrWO4 as a phosphor, green and red phosphors were synthesized by doping with Tb3+ and Eu3+ rare earth ions. The synthesized samples had a tetragonal [...] Read more.
Crystalline SrWO4 was synthesized at room temperature using a co-precipitation method. To use the SrWO4 as a phosphor, green and red phosphors were synthesized by doping with Tb3+ and Eu3+ rare earth ions. The synthesized samples had a tetragonal structure, and the main peak (112) phase was clearly observed. When the sample was excited using the absorption peak observed in the ultraviolet region, SrWO4:Tb3+ showed an emission spectrum of 544 nm, and SrWO4:Eu3+ showed an emission spectrum of 614 nm. When Tb3+ and Eu3+ ions were co-doped to realize various colors, a yellow-emitting phosphor was realized as the doping concentration of Eu3+ ions increased. When the synthesized phosphor was scattered on a glass substrate with fingerprints, as used in the field of fingerprint recognition, the fingerprint was revealed by green, red, and yellow emissions in response to a UV lamp. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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11 pages, 4253 KiB  
Article
Preparation of Cerium Oxide via Microwave Heating: Research on Effect of Temperature Field on Particles
by Chao Lv, Hong-Xin Yin, Yan-Long Liu, Xu-Xin Chen, Ming-He Sun and Hong-Liang Zhao
Crystals 2022, 12(6), 843; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12060843 - 15 Jun 2022
Cited by 2 | Viewed by 1541
Abstract
Micro–nano cerium oxide particles with regular morphology and good dispersity have been widely used in polishing and other industrial fields. Microwave heating is an effective, controllable and green heating technology. The Venturi reactor used for microwave heating developed by our team was the [...] Read more.
Micro–nano cerium oxide particles with regular morphology and good dispersity have been widely used in polishing and other industrial fields. Microwave heating is an effective, controllable and green heating technology. The Venturi reactor used for microwave heating developed by our team was the core equipment utilized to study the effects of pyrolysis conditions on the purity and microstructure of cerium oxide particles. The experiments were carried out and the products were characterized using XRD, SEM and EDS. Microwave heating, fluid flow and chemical reaction were coupled using numerical simulation, the effects of microwave power, reactor location and waveguide arrangement on temperature fields were investigated. The results showed that with the microwave power increasing, the degree of crystallinity and purity of cerium oxide improved. The morphology gradually became sphere-like. Varied reactor locations and waveguide arrangements changed the gradient and dispersity of temperature fields. Bulk particles and agglomeration could be avoided, and cerium oxide particles with average size of 80 nm were produced when the reactor was located in the center of the cavity. Vertical arrangement of waveguides had the advantages of higher temperature value, gentle gradient and better dispersity. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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11 pages, 2666 KiB  
Article
Photoluminescence of the Eu3+-Activated YxLu1−xNbO4 (x = 0, 0.25, 0.5, 0.75, 1) Solid-Solution Phosphors
by Milica Sekulić, Tatjana Dramićanin, Aleksandar Ćirić, Ljubica Đačanin Far, Miroslav D. Dramićanin and Vesna Đorđević
Crystals 2022, 12(3), 427; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12030427 - 19 Mar 2022
Cited by 7 | Viewed by 1962
Abstract
Eu3+-doped YxLu1−xNbO4 (x = 0, 0.25, 0.5, 0.75, 1) were prepared by the solid-state reaction method. YNbO4:Eu3+ and LuNbO4:Eu3+ crystallize as beta-Fergusonite (SG no. 15) in 1–10 μm diameter particles. [...] Read more.
Eu3+-doped YxLu1−xNbO4 (x = 0, 0.25, 0.5, 0.75, 1) were prepared by the solid-state reaction method. YNbO4:Eu3+ and LuNbO4:Eu3+ crystallize as beta-Fergusonite (SG no. 15) in 1–10 μm diameter particles. Photoluminescence emission spectra show a slight linear variation of emission energies and intensities with the solid-solution composition in terms of Y/Lu content. The energy difference between Stark sublevels of 5D0→7F1 emission increases, while the asymmetry ratio decreases with the composition. From the dispersion relations of pure YNbO4 and LuNbO4, the refractive index values for each concentration and emission wavelength are estimated. The Ω2 Judd–Ofelt parameter shows a linear increase from 6.75 to 7.48 × 10−20 cm2 from x = 0 to 1, respectively, and Ω4 from 2.69 to 2.95 × 10−20 cm2. The lowest non-radiative deexcitation rate was observed with x = 1, and thus LuNbO4:Eu3+ is more efficient phosphor than YNbO4:Eu3+. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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14 pages, 5846 KiB  
Article
Low-Temperature Magnetic and Magnetocaloric Properties of Manganese-Substituted Gd0.5Er0.5CrO3 Orthochromites
by Neeraj Panwar, Kuldeep Singh, Komal Kanwar, Yugandhar Bitla, Surendra Kumar and Venkata Sreenivas Puli
Crystals 2022, 12(2), 263; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst12020263 - 15 Feb 2022
Cited by 7 | Viewed by 2443
Abstract
Rare-earth chromites have been envisioned to replace gas-based refrigeration technology because of their promising magnetocaloric properties at low temperatures, especially in the liquid helium temperature range. Here, we report the low-temperature magnetic and magnetocaloric properties of Gd0.5Er0.5Cr1−xMn [...] Read more.
Rare-earth chromites have been envisioned to replace gas-based refrigeration technology because of their promising magnetocaloric properties at low temperatures, especially in the liquid helium temperature range. Here, we report the low-temperature magnetic and magnetocaloric properties of Gd0.5Er0.5Cr1−xMnxO3 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) rare-earth orthochromites. The Néel transition temperature (TN) was suppressed from 144 K for Gd0.5Er0.5CrO3 to 66 K for the Gd0.5Er0.5Cr0.5Mn0.5O3 compound. Furthermore, magnetization reversal was observed in the magnetization versus temperature behavior of the Gd0.5Er0.5Cr0.6Mn0.4O3 and Gd0.5Er0.5Cr0.5Mn0.5O3 compounds at 100 Oe applied magnetic field. The magnetic entropy change (−∆S) value varied from 16.74 J/kg-K to 7.46 J/kg-K, whereas the relative cooling power (RCP) ranged from 375.94 J/kg to 220.22 J/kg with a Mn ion concentration at 5 T field and around 7.5 K temperature. The experimental results were substantiated by a theoretical model. The present values of the magnetocaloric effect are higher than those of many undoped chromites, manganites and molecular magnets in the liquid helium temperature range. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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19 pages, 10588 KiB  
Article
Thermal Stability and Radiation Tolerance of Lanthanide-Doped Cerium Oxide Nanocubes
by Kory Burns, Paris C. Reuel, Fernando Guerrero, Eric Lang, Ping Lu, Assel Aitkaliyeva, Khalid Hattar and Timothy J. Boyle
Crystals 2021, 11(11), 1369; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11111369 - 11 Nov 2021
Cited by 4 | Viewed by 2808
Abstract
The thermal and radiation stability of free-standing ceramic nanoparticles that are under consideration as potential fillers for the improved thermal and radiation stability of polymeric matrices were investigated by a set of transmission electron microscopy (TEM) studies. A series of lanthanide-doped ceria (Ln:CeO [...] Read more.
The thermal and radiation stability of free-standing ceramic nanoparticles that are under consideration as potential fillers for the improved thermal and radiation stability of polymeric matrices were investigated by a set of transmission electron microscopy (TEM) studies. A series of lanthanide-doped ceria (Ln:CeOx; Ln = Nd, Er, Eu, Lu) nanocubes/nanoparticles was characterized as synthesized prior to inclusion into the polymers. The Ln:CeOx were synthesized from different solution precipitation (oleylamine (ON), hexamethylenetetramine (HMTA) and solvothermal (t-butylamine (TBA)) routes. The dopants were selected to explore the impact that the cation has on the final properties of the resultant nanoparticles. The baseline CeOx and the subsequent Ln:CeOx particles were isolated as: (i) ON-Ce (not applicable), Nd (34.2 nm), Er (27.8 nm), Eu (42.4 nm), and Lu (287.4 nm); (ii) HMTA-Ce (5.8 nm), Nd (6.6 nm), Er (370.0 nm), Eu (340.6 nm), and Lu (287.4 nm); and (iii) TBA-Ce (4.1 nm), Nd (5.0 nm), Er (3.8 nm), Eu (7.3 nm), and Lu (3.8 nm). The resulting Ln:CeOx nanomaterials were characterized using a variety of analytical tools, including: X-ray fluorescence (XRF), powder X-ray diffraction (pXRD), TEM with selected area electron diffraction (SAED), and energy dispersive X-ray spectroscopy (EDS) for nanoscale elemental mapping. From these samples, the Eu:CeOx (ON, HMTA, and TBA) series were selected for stability studies due to the uniformity of the nanocubes. Through the focus on the nanoparticle properties, the thermal and radiation stability of these nanocubes were determined through in situ TEM heating and ex situ TEM irradiation. These results were coupled with data analysis to calculate the changes in size and aerial density. The particles were generally found to exhibit strong thermal stability but underwent amorphization as a result of heavy ion irradiation at high fluences. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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9 pages, 3949 KiB  
Article
Calcium Tungstate Doped with Rare Earth Ions Synthesized at Low Temperatures for Photoactive Composite and Anti-Counterfeiting Applications
by Soung-Soo Yi and Jae-Yong Jung
Crystals 2021, 11(10), 1214; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11101214 - 08 Oct 2021
Cited by 10 | Viewed by 2691
Abstract
A precursor was prepared using a co-precipitation method to synthesize crystalline calcium tungstate. The prepared precursor was dried in an oven at 80 °C for 18 h. The dried powders, prepared without a heat treatment process, were observed in XRD analysis to be [...] Read more.
A precursor was prepared using a co-precipitation method to synthesize crystalline calcium tungstate. The prepared precursor was dried in an oven at 80 °C for 18 h. The dried powders, prepared without a heat treatment process, were observed in XRD analysis to be a crystalline CaWO4 phase, confirming that the synthesis of crystalline CaWO4 is possible even at low temperature. To use this crystalline CaWO4 as a light emitting material, rare earth ions were added when preparing the precursor. The CaWO4 powders doped with terbium (Tb3+) and europium (Eu3+) ions, respectively, were also observed to be crystalline in XRD analysis. The luminescence of the undoped CaWO4 sample exhibited a wide range of 300~600 nm and blue emission with a central peak of 420 nm. The Tb3+-doped sample showed green light emission at 488, 545, 585, and 620 nm, and the Eu3+-doped sample showed red light emission at 592, 614, 651, and 699 nm. Blue, green, and red CaWO4 powders with various luminescence properties were mixed with glass powder and heat-treated at 600 °C to fabricate a blue luminescent PiG disk. In addition, a flexible green and red light-emitting composite was prepared by mixing it with a silicone-based polymer. An anti-counterfeiting application was prepared by using the phosphor in an ink, which could not be identified with the naked eye but can be identified under UV light. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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9 pages, 2634 KiB  
Article
Charge Compensation in Europium-Doped Hafnia Nanoparticles: Solvothermal Synthesis and Colloidal Dispersion
by Xavier H. Guichard, Francesco Bernasconi and Alessandro Lauria
Crystals 2021, 11(9), 1042; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11091042 - 30 Aug 2021
Cited by 2 | Viewed by 2142
Abstract
Effective charge compensation of europium in hafnium oxide nanoparticles was achieved at low temperature, allowing high doping incorporation (up to 6 at.%) and enhanced luminescence. The efficiency of the incorporation and charge compensation was confirmed by scanning electron microscope energy dispersive X-ray spectroscopy [...] Read more.
Effective charge compensation of europium in hafnium oxide nanoparticles was achieved at low temperature, allowing high doping incorporation (up to 6 at.%) and enhanced luminescence. The efficiency of the incorporation and charge compensation was confirmed by scanning electron microscope energy dispersive X-ray spectroscopy and powder X-ray diffraction measurements. Despite the known polymorphism of hafnium oxide, when doped to a concentration above 3 at.%, only the pure monoclinic phase was observed up to 6 at.% of europium. Furthermore, the low-temperature solvothermal route allowed the direct formation of stable dispersions of the synthesized material over a wide range of concentrations in aqueous media. The dispersions were studied by diffuse light scattering (DLS) to evaluate their quality and by photoluminescence to investigate the incorporation of the dopants into the lattice. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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8 pages, 2131 KiB  
Article
Heat-Induced Transformation of Luminescent, Size Tuneable, Anisotropic Eu:Lu(OH)2Cl Microparticles to Micro-Structurally Controlled Eu:Lu2O3 Microplatelets
by Madeleine Fellner, Alberto Soppelsa and Alessandro Lauria
Crystals 2021, 11(8), 992; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11080992 - 20 Aug 2021
Viewed by 1637
Abstract
Synthetic procedures to obtain size and shape-controlled microparticles hold great promise to achieve structural control on the microscale of macroscopic ceramic- or composite-materials. Lutetium oxide is a material relevant for scintillation due to its high density and the possibility to dope with rare [...] Read more.
Synthetic procedures to obtain size and shape-controlled microparticles hold great promise to achieve structural control on the microscale of macroscopic ceramic- or composite-materials. Lutetium oxide is a material relevant for scintillation due to its high density and the possibility to dope with rare earth emitter ions. However, rare earth sesquioxides are challenging to synthesise using bottom-up methods. Therefore, calcination represents an interesting approach to transform lutetium-based particles to corresponding sesquioxides. Here, the controlled solvothermal synthesis of size-tuneable europium doped Lu(OH)2Cl microplatelets and their heat-induced transformation to Eu:Lu2O3 above 800 °C are described. The particles obtained in microwave solvothermal conditions, and their thermal evolution were studied using powder X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical microscopy, thermogravimetric analysis (TGA), luminescence spectroscopy (PL/PLE) and infrared spectroscopy (ATR-IR). The successful transformation of Eu:Lu(OH)2Cl particles into polycrystalline Eu:Lu2O3 microparticles is reported, together with the detailed analysis of their initial and final morphology. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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19 pages, 1729 KiB  
Article
Luminescence Intensity Ratio Thermometry with Er3+: Performance Overview
by Aleksandar Ćirić, Tamara Gavrilović and Miroslav D. Dramićanin
Crystals 2021, 11(2), 189; https://0-doi-org.brum.beds.ac.uk/10.3390/cryst11020189 - 14 Feb 2021
Cited by 34 | Viewed by 4391
Abstract
The figures of merit of luminescence intensity ratio (LIR) thermometry for Er3+ in 40 different crystals and glasses have been calculated and compared. For calculations, the relevant data has been collected from the literature while the missing data were derived from available [...] Read more.
The figures of merit of luminescence intensity ratio (LIR) thermometry for Er3+ in 40 different crystals and glasses have been calculated and compared. For calculations, the relevant data has been collected from the literature while the missing data were derived from available absorption and emission spectra. The calculated parameters include Judd–Ofelt parameters, refractive indexes, Slater integrals, spin–orbit coupling parameters, reduced matrix elements (RMEs), energy differences between emitting levels used for LIR, absolute, and relative sensitivities. We found a slight variation of RMEs between hosts because of variations in values of Slater integrals and spin–orbit coupling parameters, and we calculated their average values over 40 hosts. The calculations showed that crystals perform better than glasses in Er3+-based thermometry, and we identified hosts that have large values of both absolute and relative sensitivity. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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