Search Results (130)

Fine powders of erbium niobate-tantalates ErNb_xTa_1−xO₄ (x = 0; 0.1; 0.3; 0.5; 0.7; 0.9; 1) have been synthesized by the liquid-phase method in this study. Ceramic samples have been prepared using conventional sintering from these powders. Rietveld refinement of XRD patterns of polycrystals determined the phase composition and clarified the parameters of the phase structure of ErNb_xTa_1−xO₄ solid solutions depending on the Nb/Ta ratio. The morphological features of the microstructure of erbium niobate-tantalate ceramics have been studied. Their mechanical properties, strength characteristics (Young’s modulus, microhardness) and critical stress intensity factor of the first kind K_IC have been estimated. The photoluminescent properties of ceramic solid solutions of erbium niobate-tantalates depending on the composition have been studied. Dark and photoinduced toxicity of finely dispersed ErNbO₄ powders have been studied in relation to Gram-positive, Gram-negative and spore-forming microorganisms. The best indicators of antibacterial activity of ErNbO₄ have been demonstrated in relation to Gram-positive cells of Micrococcus sp. The discovered properties open up the possibility of not only traditional use as functional materials, but also the use of these materials for disinfection of surfaces, water and biological tissues. Full article

The present study presents a comparative evaluation of two analytical deconvolution models applied to Optically Stimulated Luminescence (OSL) decay curves of zirconia-reinforced lithium silicate (ZLS), a glass-ceramic material with potential applications in accidental dosimetry. ZLS samples were subjected to beta irradiation and measured under Continuous Wave OSL (CW-OSL) protocols. A comparative analysis is conducted between two deconvolution approaches—the General Order Kinetics (GOK) model and a master analytical equation based on the Lambert W function. The results imply that both models yield a linear dose-response behavior of the fast OSL component; however, the Lambert W approach offers simpler fitting with fewer parameters. The abovementioned findings demonstrate the methodological robustness of the Lambert W formalism and also confirm that ZLS is a promising dosimetric material, aligning with the goals of protocol development in material characterization. Full article

This study examines the impact of varying the content of lanthanum oxide and lanthanum fluoride on the formation of glass-ceramics and their effect on the thermal stability of Na-aluminosilicate glasses, depending on the type and concentration of the raw material used. The aim of this study is to obtain a fluoride crystalline phase in the glassy matrix. Such a phase, due to its low phonon energy, increases the probability of radiative transitions (decay) of optically active lanthanide dopants, thereby enhancing luminescence. The scope of the work included the preparation of two glass series with varying amounts of La₂O₃ and LaF₃ to determine the glass-forming range and to identify the characteristic temperatures of the glasses using Differential Thermal Analysis. It was found that increasing the La₂O₃ content above 10 mol% in this glass leads to exceeding the target melting temperature (1400 °C) of the glass batch. In contrast, the introduction of 10 mol% LaF₃ prevents the formation of homogeneous glass. Based on these results, a controlled crystallization process was designed, and the resulting crystalline phases were identified using X-ray diffraction (XRD). In the base glass, two crystalline phases were identified: Na₂O·Al₂O₃·SiO₂ and Na₂SiO₃. For the La-oxide series, the crystallization of NaAlSiO₄ and La₂SiO₅ was confirmed. In the case of the La-fluoride series, the formation of LaF₃ was observed. It was found that by introducing an appropriate amount of LaF₃ (7.5 mol%) into the aluminosilicate network, it is possible to obtain a glass suitable for controlled crystallization, leading to the formation of a low-phonon LaF₃ phase. Full article

(Y_xGd_3−x)(Al_yGa_5−y)O₁₂:Ce and (Lu_xGd_3−x)(Al_yGa_5−y)O₁₂:Ce ceramics were synthesized for the first time by direct exposure of a powerful electron flux to a mixture of the corresponding oxide components. Five-component ceramics were obtained from oxide powders of Y₂O₃, Lu₂O₃, Gd₂O₃, Al₂O₃, Ga₂O₃, and Ce₂O₃ in less than 1 s, without the use of any additional reagents or process stimulants. The average productivity of the synthesis process was approximately 5 g/s. The reaction yield, defined as the mass ratio of the synthesized ceramic to the initial mixture, ranged from 94% to 99%. The synthesized ceramics exhibit photoluminescence when excited by radiation in the 340–450 nm spectral range. The position of the luminescence bands depends on the specific composition, with the emission maxima located within the 525–560 nm range. It is suggested that under high radiation power density, the element exchange rate between the particles of the initial materials is governed by the formation of an ion–electron plasma. Full article

The aim of this study was to investigate the possibility of Ag nanoparticle crystallization in B₂O₃–Bi₂O₃ glass using a heat treatment method and to investigate the possible influence of the obtained nanoparticles on the emission intensity of Eu³⁺ ions. Borate–bismuth glasses with different B₂O₃:Bi₂O₃ molar ratios of 50:50, 60:40 and 70:50 with Ag and Eu³⁺ ions were successfully synthesized. The structure of the glasses was studied using XRD and FTIR methods. The XRD results exhibited a characteristic amorphous halo, confirming the absence of long-range order in the samples. The glass transition temperatures of various compositions, required to select the annealing temperature, were measured using DTA analysis. The strong maximum in the UV–Vis spectrum of the sample with the highest Bi₂O₃ content clearly indicated the presence of Ag nanoparticles in the glass. Moreover, a color change was observed for this sample, from slightly yellow to red. The presence of Ag nanoparticles was further confirmed via TEM and XPS studies. However, with a high content of Ag nanoparticles in the matrix, their positive effect on luminescence intensity was not observed. The obtained results show that B₂O₃–Bi₂O₃ glass and glass ceramics, with Ag nanoparticles and rare-earth (Re) ions, could be considered as a new phosphor for light-emitting diodes (LEDs). Full article

Yttrium oxide ceramic is an excellent optical material widely used in lasers, scintillators, and upconversion luminescence. In this study, LiF was employed as an additive to generate volatile gases (CF)_n to effectively inhibit carbon contamination and act as a sintering aid to accelerate densification during the spark plasma sintering (SPS) process. The effects of sintering temperature and annealing time on the transmittance of Y_1.8La_0.2O₃ transparent ceramics were systematically investigated. Results indicate that excessive LiF addition reduces the transmittance of Y_1.8La_0.2O₃ transparent ceramics due to the precipitation of F⁻ ions at grain boundaries, forming a secondary phase. For the Y_1.8La_0.2O₃ ceramics with 0.3 wt.% LiF, transmittance initially increases and then decreases with rising sintering temperature, reaching a maximum value of 78.10% in the UV region at 1550 °C. Under these conditions, the average particle size and relative density are 10–30 μm and 99.36%, respectively. Oxygen vacancies within the ceramics act as defects that degrade transmittance. Proper annealing in air reduces oxygen vacancy content, thereby improving transmittance. After annealing at 900 °C for 3 h, the maximum transmittance of Y_1.8La_0.2O₃ ceramics with 0.3 wt.% LiF increases to 82.67% in the UV region, accompanied by a 5.68% reduction in oxygen vacancy concentration. Full article

This paper demonstrates the application of eutectic welding to Ce³⁺:YAG transparent ceramics for reliable detection and imaging of UV emission, particularly focusing on demanding conditions, such as high repetition rate, high energy, and high vacuum. A series of Ce³⁺:YAG transparent ceramics with different Ce³⁺ doping concentrations (0.1 at%, 0.3 at%, 0.5 at%, and 1.0 at%) were prepared via vacuum sintering. Their crystal microstructure, luminescence properties, transmittance, and fluorescence lifetime were studied. It was found that the optimal Ce³⁺ doping concentration is 0.3 at%. The measured ultraviolet-to-visible energy conversion efficiency of the 0.3 at% Ce³⁺:YAG transparent ceramics with a thickness of 1.0 mm is 3.9%. Compared with silicone encapsulated Ce³⁺:YAG transparent ceramic samples, the eutectic-soldered samples exhibited excellent resistance to temperature quenching of the luminescence, which indicates that eutectic welding can effectively improve the fluorescence performance of Ce³⁺:YAG transparent ceramics for the application of deep ultraviolet light detection. Full article

This paper presents the results of complementary experimental (electron microscopy, X-ray diffraction, diffuse reflectance, photoluminescence (PL), and FTIR spectroscopy) and computational (molecular dynamics and DFT-based electronic structural) studies of oxide glasses of xP₂O₅-yMoO₃-zBi₂O₃-(1-x-y-z)K₂O systems and glass-ceramics based on these (crystal @glass), where the KBi(MoO₄)₂ complex oxide is the crystal component (KBi(MoO₄)₂ @glass). The behavior of the observed PL characteristics is analyzed in synergy with the results of the calculations of their atomic structures and changes in the oxygen environment of bismuth atoms during the transition crystal → interphase → glass. It is shown that the optical absorption and PL characteristics of such systems are largely determined by the content of Bi₂O₃ and MoO₃ oxides in the initial charge and by the content of bismuth ions in different charge states that exist in the produced glass and glass-ceramics. It was found that the blue PL (spectral range 375–550 nm) of both the glasses and the glass-ceramics originated from radiative transitions ³P₁ → ¹S₀ in Bi³⁺ bismuth ions. The yellow-red PL (range 550–850 nm) was mainly associated with the luminescence of bismuth ions in lower charge states, Bi²⁺, Bi⁺, and Bi⁰. The thickness of the interphase layers of glass-ceramics was estimated to be 1.5–2.0 nm. It was found that the changes in the spectra of optical absorption and the PL/PL excitation of the glass-ceramics occurred due to the decrease in the number of oxygen atoms in the nearest surrounding bismuth ions in the interphase region. These changes can be used for the spectral probing of the formation and presence of interphase layers. Full article

In this paper, the crystallization behavior of 52WO₃:22B₂O₃:26La₂O₃:0.5Eu₂O₃ glass has been investigated in detail by XRD and TEM analysis. The luminescent properties of the resulting glass-ceramics were also investigated. By XRD and TEM analysis, crystallization of β-La₂W₂O₉ and La₂WO₆ crystalline phases has been proved. Photoluminescent spectra showed increased emission in the resulting glass-ceramic samples compared to the parent glass sample due to higher asymmetry of Eu³⁺ ions in the obtained crystalline phases, where the active Eu³⁺ ions are incorporated. Also, in the glass-ceramics, the crystalline particles are embedded in the amorphous matrix and more of them are separated from each other which improves the light scattering intensity from the free interfaces of the nanocrystallites, resulting in the enhancement of the PL intensity. It was established that the optimum emission intensity is registered for glass-ceramic samples obtained after an 18 h heat treatment of the parent glass. After 21 h of glass crystallization, the amount of crystallite particles is high enough, and they are in close proximity to each other, and hence, the average distance between europium ions decreases, resulting in quenching of Eu³⁺ and a decrease in the emission intensity. Additionally, at 21 h of glass crystallization, formation of new crystalline phase—La₂WO₆ is established. A redistribution of Eu³⁺ ions in the different crystalline compounds is most likely taking place, which is also not favorable for the emission intensity. Full article

The luminescence properties of BaMgF₄ ceramics synthesized using electron beam-assisted synthesis were investigated under vacuum ultraviolet (VUV) synchrotron excitation at a cryogenic temperature of T = 9 K. Their excitation spectra, measured over the 4–10.8 eV range, and corresponding luminescence spectra revealed a complex multicomponent structure with emission maxima at 3.71, 3.55, 3.33, 3, and ~2.8 eV. The primary luminescence band at 330 nm was attributed to self-trapped excitons (STE) excited near the band edge (9.3–9.7 eV), indicating interband transitions and subsequent excitonic relaxation. Bands at 3 and ~2.8 eV were associated with defect states efficiently excited at 6.45 eV, 8 eV and high-energy transitions near 10.3 eV. The excitation spectrum showed distinct maxima at 5, 6.45, and 8 eV, which were interpreted as excitations of defect-related states. These results highlight the interplay between interband transitions, excitonic processes, and defect-related luminescence, which defines the complex dynamics of BaMgF₄ ceramics. These findings confirm that radiation synthesis introduces defect centers influencing luminescent properties, making BaMgF₄ a promising material for VUV and UV applications. Full article

A transparent fluoroborosilicate glass ceramic was designed for the controllable precipitation of fluoride nanocrystals and to greatly enhance the photoluminescence of active ions. Through the introduction of B₂O₃ into fluorosilicate glass, the melting temperature was decreased from 1400 to 1050 °C, and the abnormal crystallization in the fabrication process of fluorosilicate glass was avoided. More importantly, the controlled crystallizations of KZnF₃ and KYb₃F₁₀ in fluoroborosilicate glass ceramics enhanced the emission of Mn²⁺ and Mn²⁺–Yb³⁺ dimers by 6.7 and 54 times, respectively. Moreover, the upconversion emission color of glass ceramic could be modulated from yellow to white and blue by adjusting the Yb³⁺ concentration. The well-designed glass ceramic is a novel and significant compound to simultaneously provide efficiently coordinated sites for transition metal and rare earth ions. More importantly, the design strategy opens a new way for engineering high-quality oxy-fluoride glass ceramics with properties of excellent stability, controllable nano-crystallization and high-efficiency photoluminescence. Full article

Electron-trapping materials have attracted a lot of attention in the field of optical data storage. However, the lack of suitable trap levels has hindered its development and application in the field of optical data storage. Herein, Lu₃Al₅O₁₂:Ce³⁺ fluorescent ceramics were developed as the optical storage medium, and high-temperature vacuum sintering induced the formation of deep traps (1.36 eV). The matrix based on the garnet-structured material ensures excellent rewritability. By analyzing the thermoluminescence and photostimulable luminescence, it is found that the transition of electrons provided by Ce³⁺ between the conduction band and trap levels offers the possibility for optical data storage. As evidence of its application, the optical information encoding using 254 nm light and decoding using a light stimulus and thermal stimulus were applied. These findings are expected to provide candidate material for novel optical storage technology, and further promote the development of advanced information storage technology. Full article

This paper presents the initial results of the synthesis of β-Ga₂O₃ luminescent ceramics via plasma gas-thermal spraying synthesis, where low-temperature plasma of an argon and nitrogen mixture was employed. A direct current electric arc generator of high-enthalpy plasma jet with a self-aligning arc length and an expanding channel of an output electrode served as a plasma source. The feedstock material consisted of a polydisperse powder of monocrystalline β-Ga₂O₃ with particle sizes ranging from 5 to 50 μm. The study presents the results of both theoretical and experimental studies on the heating rate and average temperature of gallium oxide particles in a plasma jet. The results of computational modelling of the synthesis process of β-Ga₂O₃ via plasma gas-thermal spraying are shown. The obtained ceramic samples were characterized using scanning electron microscopy and X-ray diffraction analysis. Our results indicate that the synthesis process yielded ceramics with a layered texture. The stoichiometric composition of ceramics exhibited a shift towards gallium-rich content. X-ray diffraction data demonstrated a reduction in the lattice parameters and unit cell volume of β-Ga₂O₃ ceramic structure. Radioluminescence spectra of β-Ga₂O₃ ceramics revealed an intensive emission band with a maximum at ~360 nm and non-exponential decay. The synthesized β-Ga₂O₃ ceramics possess potential applications in scintillation detectors. Full article

This study compared the chemical, structural, and luminescent properties of xerogel-based ceramic powders (CPs) with those of a new series of crystallized aerogels (CAs) synthesized by the epoxy-assisted sol–gel process. Materials with different proportions of Eu³⁺ (2, 5, 8, and 10 mol%) were synthesized in Lu₂O₃ host matrices, as well as a Eu₂O₃ matrix for comparative purposes. The products were analyzed by infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), photoluminescence analysis, and by the Brunauer–Emmett–Teller (BET) technique. The results show a band associated with the M-O bond, located at around 575 cm⁻¹. XRD enabled us to check two ensembles: matrices (Lu₂O₃ or Eu₂O₃) and doping (Lu₂O₃:Eu³⁺) with appropriate chemical compositions featuring C-type crystal structures and intense reflections by the (222) plane, with an interplanar distance of around 0.3 nm. Also, the porous morphology presented by the materials consisted of interconnected particles that formed three-dimensional networks. Finally, emission bands due to the energy transitions (⁵D_J, where J = 0, 1, 2, and 3) were caused by the Eu³⁺ ions. The samples doped at 10 mol% showed orange-pink photoluminescence and had the longest disintegration times and greatest quantum yields with respect to the crystallized Eu₂O₃ aerogel. Full article

The first experimental results obtained by the ion beam-induced luminescence technique from the ceramic bodies of ancient tiles are reported in this work. The photon emission from the ceramic bodies is related to the starting minerals and the manufacturing conditions, particularly the firing temperature and cooling processes. Moreover, the results indicate that this non-destructive technique, performed under a helium-rich atmosphere instead of an in-vacuum setup and with acquisition times of only a few seconds, presents a promising alternative to traditional, often destructive, compositional characterisation methods. Additionally, by adding other ion beam-based techniques such as PIXE (Particle-Induced X-ray Emission) and PIGE (Particle-Induced Gamma-ray Emission), compositional information from light elements such as Na can also be inferred, helping to also identify the raw materials used. Full article