Doped Yttrium Aluminum Garnet Research Articles

Analysis of Er3+ diffusion within transparent YAG ceramics manufactured through various routes by SPS

Different bonding approaches were considered to develop layered composite ceramics of erbium doped yttrium aluminium garnet (Er:YAG/YAG) by Spark Plasma Sintering. More precisely three different strategies were envisaged, starting either from a stack of powders, pre-sintered or sintered ceramics. Highlighted by Electron Probe Micro Analysis (EPMA) analyses, these approaches led to different designs of interface i.e. doping profiles, linked to the different thermo-mechanical treatments applied, which have an influence on the grain boundary diffusion of erbium ions. The lengths of the diffusion were found to be of 12 μm, 63 μm and 140 μm respectively for fully dense, powder and pre-sintered assembly approaches.

Influencing effects of variant laser pulse energy on fatigue behavior induced by LSP

The set objective in this study is to understand the effects of laser shock processing of variant laser pulse energies on residual compressive stress, microhardness, fatigue fracture and fatigue life in the application of aircraft lug material. The effects of three variant laser pulse energies of 3.0, 4.0 and 5.7 J were examined along with laser processing parameters. A Q-switch (neodymium (Nd)-doped yttrium aluminum garnet) laser system was used in this experiment with a wavelength, a pulse width, a spot diameter and an overlapping ratio of 1046 nm, 10 nm, 3 mm and 50%, respectively. After laser shock peening (LSP), the superficial layer stress state showed varied results from tensile to residual stress of 50 to −225, −260 and −301 MPa after 3.0, 4.0 and 5.7 J, respectively. The microhardness of the as-received specimen was 137 HV. However, after LSP, it increased to 198, 210 and 223 HV, respectively. The fatigue life performance also significantly increased up to 53 371 (2 × 105) cycles.

Embedding of Y3Al5O12:Ce within 316L stainless steel parts by laser powder bed fusion as an efficient luminescent sensor

Transition to circular economy requires the production of sustainable and eco-designed materials that help to reduce environmental impacts of metallic components. The development of sensing layers providing luminescent tracking functionalities is a potential method for extending the service life of metallic parts. In this study, incorporation of luminescent Ce3+ doped yttrium aluminum garnet (YAG:Ce) within a stainless steel 316L (SS316L) matrix has been achieved for the first time by laser powder bed fusion (L-PBF). Embedding of phosphor particles was successfully carried out on a selected area of the 3D printed sample. Despite harsh processing conditions of L-PBF, luminescent emission was detected by optical spectroscopy. Microstructure and chemical composition of the incorporation zone were investigated in order to better understand optical properties. The precipitated particles exhibit new optical features, arising from the modification of the luminescent host lattice and the intricate interactions with the metal matrix.

Coherent control of the photonic spin Hall effect by Er3+ ion concentration in an Er3+-doped YAG crystal

We theoretically investigate the effect of doped Er3+ ion concentration on the spin Hall effect (SHE) of light reflected from a Kretschmann-Raether (K-R) structure. In such a structure, an Er3+-doped yttrium aluminum garnet (YAG) crystal acts as the substrate. The excitation of surface plasmon resonance(SPR) leads to the enhancement of the spin splitting of the reflected beam in the resonance reflection dip. Due to the variation of electric dipole moment and energy level lifetime induced by Er3+ ion concentration, the spin-dependent transverse shift is sensitively dependent upon Er3+ ion concentration. Furthermore, under different concentrations of Er3+ ion, the intensity and detuning of the control field have different effects on the magnitude, sign and position of the transverse shift. More importantly, the photonic SHE can be significantly enhanced via choosing the suitable values of the control intensity and detuning at 15% Er3+ ion concentration. Therefore, our scheme may provide a basis for selecting suitable Er3+ ion concentration to enhance the SHE of light in future integrated systems.

Changes in melanocytic nevi treated with laser hair removal: A systematic review.

Incidental treatment of melanocytic nevi during laser hair removal (LHR) has been noted to cause clinical and dermoscopic changes that may appear similar to findings seen in atypical or neoplastic melanocytic lesions. The rate and characteristics of these changes has not been well-studied. The objective of this review article is to assess the literature for reported changes in melanocytic nevi following LHR to guide clinical practice. PubMed was searched December 5, 2022 for articles evaluating changes in melanocytic nevi after LHR treatment using the following search terms: "nevi laser hair removal," "nevi diode," "nevi long pulse alexandrite," "nevi long pulse neodymium doped yttrium aluminum garnet," and "melanoma laser hair removal." All English language patient-based reports discussing incidental treatment of melanocytic nevi while undergoing LHR with a laser were eligible for inclusion, while reports of changes following hair removal with non-laser devices such as intense pulsed light were excluded. Studies evaluating non-melanocytic nevi such as Becker's nevus or nevus of Ota were excluded as were those evaluating the intentional ablation or removal of melanocytic lesions. Ten relevant studies were included, consisting of seven case reports or series and three observational trials, two of which were prospective and one retrospective. Among the seven case reports or series there were a total of 11 patients, six of which had multiple affected nevi. Clinical and dermoscopic changes to nevi following LHR appear to be common in clinical practice, though not well studied. Clinical and dermoscopic changes have been noted to present as early as 15 days after treatment and persist to the maximum time of follow up at 3 years. Commonly reported changes include regression, decreased size, laser induced asymmetry, bleaching, darkening, and altered pattern on dermoscopy. Histologic changes include mild atypia, thermal damage, scar formation, and regression. Although some of the clinical and dermoscopic alterations may be concerning for malignancy, to our knowledge, there are no documented cases of malignant transformation of nevi following treatment with LHR. This study is limited by the low number of relevant reports and their generally small sample size, many of which is limited to single cases. Additionally, comparison of available data was limited by variable reporting of treatment regimens and outcomes. Changes to nevi treated during LHR are not uncommon. Modifications to nevi may occur and look similar to changes seen in dysplastic or neoplastic melanocytic lesions. Notably, despite the widespread use of LHR since the first device was Food and Drug Administration approved in 1995, a time span of nearly three decades, there have been no reported cases of melanoma or severe dysplastic changes within treated nevi. However, dermatologists should be aware that morphologic and dermoscopic alterations can occur after LHR to prevent unnecessary surgical procedures. Although melanoma has not been reported to occur in nevi treated with LHR nor with any other laser exposures, further long-term data is needed to fully elucidate this concern. Optimally, nevi should be examined by a dermatologist before LHR to determine a baseline clinical and dermoscopic morphology. If there is concern for potential atypia, laser should be avoided over such nevi to avoid confusion at future follow up visits.

Facile Microwave Synthesis of Efficient Green Emissive Carbon Dots Powder and Their Application in Visible Light Communication and White Light Emitting Devices

AbstractHighly green emissive solid‐state carbon dots (CDs) with photoluminescence quantum efficiency of 58% are prepared through a rapid microwave assisted heating method. Due to the spatial confinement from the biuret crystal matrix, aggregation among CDs is effectively suppressed, thus allowing the CDs to give efficient emission in the solid‐state. The CDs show excitation independent emission and mono‐exponential decay characteristics with a nearly constant lifetime of ≈13 ns upon varying the detected emissions, indicating the presence of a single type of emissive state in the CDs. Due to their high quantum efficiency and short lifetime, the obtained CDs are applied as the color conversion layer of a near‐ultraviolet micro light‐emitting diode (µLED) chip (405 nm) for visible light communication, achieving a modulation bandwidth of 165 MHz, which is much higher than the bandwidth of the conventional combination of Ce3+‐doped yttrium aluminum garnet phosphor with GaN LED. Moreover, the green emitting solid‐state CDs are applied to fabricate a prototype white LED device, which exhibits good lighting suitability with a color rendering index of 90.6 and a Commission Internationale de L'Eclairage chromaticity coordinates of (0.327, 0.332).

Role of Er3+ ion concentration on the Goos–Hänchen shift in an Er3+-doped YAG crystal

We investigate the effect of doped Er3+ ion concentration on the Goos–Hänchen (GH) shift of a reflected beam in a Kretschmann–Raether structure, where an Er3+-doped yttrium aluminum garnet crystal is employed as the substrate. Due to the difference in the electric dipole moment and spontaneous emission decay induced by Er3+ ion concentration, the reflected GH shift is sensitively dependent upon Er3+ ion concentration. Furthermore, it is demonstrated that the intensity and detuning of the control field have different effects on the magnitude, sign, and position of the GH shift under different concentrations of Er3+ ion. Therefore, our scheme may provide a basis for selecting suitable concentrations to realize high-performance optical devices in future integrated systems.

Ultra-Small YPO4 -YAG:Ce Composite Nanophosphors with a Photoluminescence Quantum Yield Exceeding 50.

Synthesis of high quality colloidal Cerium(III) doped yttrium aluminum garnet (Y3 Al5 O12 :Ce3+ , "YAG:Ce") nanoparticles (NPs) meeting simultaneously both ultra-small size and high photoluminescence (PL) performance is challenging, as generally a particle size/PL trade-off has been observed for this type of nanomaterials. The glycothermal route is capable to yield ultra-fine crystalline colloidal YAG:Ce nanoparticles with a particle size as small as 10nm but with quantum yield (QY) no more than 20%. In this paper, the first ultra-small YPO4 -YAG:Ce nanocomposite phosphor particles having an exceptional QY-to-size performance with an QY up to 53% while maintaining the particle size ≈10nm is reported. The NPs are produced via a phosphoric acid- and extra yttrium acetate-assisted glycothermal synthesis route. Localization of phosphate and extra yttrium entities with respect to cerium centers in the YAG host has been determined by fine structural analysis techniques such as X-ray diffration (XRD), solid state nuclear magnetic resonance (NMR), and high resolution scanning transmission electron microscopy (HR-STEM), and shows distinct YPO4 and YAG phases. Finally, a correlation between the additive-induced physico-chemical environment change around cerium centers and the increasing PL performance has been suggested based on electron paramagnetic resonance (EPR), X-ray photoelectronspectrometry (XPS) data, and crystallographic simulation studies.

Visible to ultraviolet C (UVC) up-conversion of Er[formula omitted] doped yttrium aluminium garnet phosphor: Antimicrobial application

In the present work, a visible to ultraviolet C (UVC) up-conversion Er3+ doped yttrium aluminium garnet (YAG) ceramic phosphor was developed by a high temperature solid state reaction method. The structural characterization of the prepared phosphor was carried out using X-ray diffraction analysis and transmission electron microscopy techniques. The up-conversion behaviour of the phosphor was studied by recording the emission spectra of the phosphor under a 460 nm blue LED source. The emission spectrum was obtained in the UV region containing peaks centred at 217, 256, 275 and 312 nm. The emitted UV radiation belongs to the germicidal UV wavelength; therefore this behaviour of the phosphor was applied for the inactivation of surface born microbes through the emitted radiation. The emission behaviour of the phosphor was further investigated by LED encapsulation. The up-conversion emission increases with an increase in the crystal size.

Acoustic Resonance Spectroscopy with an Uncalibrated Microwave Path

Acoustic resonance spectroscopy (ARS) is an informative analytical method that yields information about thicknesses and acoustic properties of layers in a multilayer structure representing a high-overtone bulk acoustic wave resonator (HBAR). Since the HBAR spectrum has many resonance features, the development of automatic methods for its processing is an urgent task. In this study, a method for extracting ARS data from a signal distorted by a RF measuring path without additional measurements of reference impedances (calibration) is proposed, which brings the spectrum to a form convenient for automatic processing and significantly expands the range of the ARS application. The method is especially relevant for processing HBAR spectra with a low excitation efficiency. As an example of such processing, the central frequencies and effective widths of more than a thousand resonant peaks are determined and, based on this, the frequency dependence of the acoustic attenuation is established for a new material: optical ceramics based on doped yttrium aluminum garnet nanoparticles.

Infrared Stimulated Luminescence of Ce3+ Doped YAG Crystals.

In this study, the infrared optically stimulated luminescence (IRSL) of single crystals of Ce3+ doped yttrium aluminum garnet (YAG) was investigated for the first time. It was found that infrared stimulation of these crystals, following previous exposure to beta radiation, produces a strong luminescence signal. The highest luminescence efficiency was exhibited by the YAG crystal with 0.1% of Ce. With this crystal, it was possible to measure as low doses as 0.1 mGy. Moreover, IRSL is mainly related to the TL peak at a relatively high temperature of c.a. 175 °C, which leads to quite good stability of the signal in time. These properties create good prospects for potential applications of YAG:Ce in dosimetric radiation measurements.

Thermochromic properties of some colored oxide materials

The thermochromic properties up to 500 °C of some colored, commercial and non-toxic oxides were studied. It includes Bi2O3, Fe2O3, In2O3, WO3, Er2O3, YAG:Ce (Ce doped yttrium aluminum garnet Y3Al5O12) and YInMn-Blue (Mn doped yttrium indium oxide YInO3). From the CIELAB colorimetric parameters (L*a*b*), evolution of the color contrast ΔE with temperature was calculated. It allowed estimating that most of these oxides change color reversibly with increasing temperature, the strongest thermochromism being found for Bi2O3 (ΔE ∼ 65 at 500 °C). Two exceptions were identified: i) Er2O3 which stayed almost identically pink with ΔE<7 even at 500 °C and ii) WO3 which original color was not recovered upon cooling back to room temperature. While the color change of the other oxides was gradual with increasing temperature, YAG:Ce compound behaved differently since its thermochromicity abruptly started above 300 °C. DSC analyses did not allow detecting any physico-chemical event in relation with these peculiarities. The obtained datasets for all these compounds can be used for anticipating the thermochromic properties of these powders and the blends made out of them.

Optimization of Pulsed Nd:YAG Laser welding for Nickel and Copper with ANFIS model

Nowadays the demand of joining dissimilar materials have increased. Pulsed Neodymium doped yttrium aluminium garnet (Nd:YAG) laser welding is in demand because of its applicability in various sectors like Automobile, Electrical and Electronic Industries. In the current investigation pulsed Nd:YAG laser welding was used to weld Nickel and Copper samples. The experimentation was conducted to study the effect of process parameters on the performance of welding and to validate numerical model. The optimization technique was employed to get optimum process parameters. The main parameters of process were current, laser focus, pulse width and frequency. The main responses plotted were Ultimate tensile stress (UTS), Hardness and Heat Affected Zone (HAZ). To perform effective experimentation design of experiment (DOE) was carried out using Taguchi method with four factors having three different levels. After experimentation Analysis of Variance (ANOVA) was employed for analysis and optimization of the effect of different parameters on the responses. Then, the Adaptive neuro fuzzy inference systems (ANFIS) model was being developed for factors and responses to get predicted results. The predicted results obtained from ANFIS model were close to experimental results.

Influence of down-shifting particle’s size on monocrystalline silicon solar cells

The potential cerium doped yttrium aluminum garnet (YAG:Ce3+) phosphor particles of different sizes are mixed with ethylene-vinyl acetate (EVA) to make luminescent downshifting films, which are then utilized for packaging monocrystalline silicon solar cells. The luminescence of YAG:Ce particles with the different diameters (3–5 µm, 5–8 µm, 8–10 µm, 10–15 µm, 15–20 µm, and 20–30 µm), the transmission of the down-shifting EVA films with the phosphor particles and performance of the packaged solar cells have been investigated. Experimental results show that the particles with 15–20 µm have the highest luminescent intensity. When the mass ratio of phosphors to EVA is fixed, the films with 20–30 µm have the highest transmission. The most significant increase in solar cell conversion efficiency after packaging is due to the downshifting EVA films with 15–20 µm particles. This research could be useful in the selection of downshifting phosphors for solar cells in the future.

Optical and structural properties of composites films based on Ce3+ -doped yttrium aluminium garnet nanoparticles embedded in polystyrene.

In the present work, attempts have been made to prepare scintillating nanoparticle composite films of Ce3+ -doped Y3 Al5 O12 (YAG:Ce) embedded in a polystyrene (PS) polymer. A YAG:Ce phosphor has been previously synthesized using the sol-gel method. YAG:Ce-PS composite films of 250 ± 30 μm thickness were prepared using a solvent casting procedure with different PS/solvent concentration and a different mass ratio between nanoparticles of YAG:Ce and PS. X-ray diffraction analysis confirmed that the YAG:Ce powders were successfully prepared. Using thermogravimetric analyses and differential scanning calorimetry, we found that the glass transition temperature (Tg) and thermal degradation were shifted to higher temperatures for composite films relative to pure PS. Photoluminescence showed the yellow emission of the Ce3+ -doped YAG phosphors, which was attributed to the 5d→4f transition of Ce3+ ion and the intensity of the emissions changed with the mass ratio of the YAG:Ce nanoparticles incorporated in the polymer and with the concentration of the polymer solution.

Investigation on the effect of vacuum annealing time on structural and optical properties of YAG:Ce nanoparticles prepared by mixed-fuel microwave solution combustion synthesis

Cerium doped yttrium aluminum garnet (YAG:Ce) nanoparticles were synthesized via mixed-fuel microwave solution combustion synthesis and further optimized by post annealing treatment. The effects of vacuum annealing time and ambient on the phosphor structural, morphological, compositional, and optical properties were investigated in detail. The structural study performed with X-ray diffraction analysis and Rietveld refinement revealed a direct crystallization from amorphous into single phase YAG:Ce was achieved at 1050 °C for 1 h. The increase in annealing time enhances the powder crystallinity and promotes crystal growth to form larger particles (50–85 nm). However, prolonged annealing would cause the partial oxidation of Ce3+ into optically inert Ce4+ ions, which was likely due to the increased Ce segregation. X-ray photoelectron spectroscopy evidenced that vacuum annealing has a higher tendency to suppress Ce3+ oxidation in comparison to air annealing, resulting in a significant enhancement of photoluminescence emission intensity by 20%. The optimum emission intensity was obtained for YAG:Ce nanoparticles after 5 h of vacuum annealing treatment with color coordinates of (0.391, 0.569). The white light emitting diode (WLED) fabricated with the optimized YAG:Ce nanoparticles showed a cool-white light with a maximum luminous efficacy of radiation of 285 lm/W and a corresponding color rendering index of 83.

Achieving Ultraviolet C and Ultraviolet B Dual‐Band Persistent Luminescence by Manipulating the Garnet Structure (Advanced Optical Materials 5/2022)

In article number 2102157, Xianli Wang and Yuanbing Mao attained persistent luminescence (PersL) with dual UVC and UVB bands with maxima at 266 and 311 nm over 12 hours upon being charged at 254 nm from Pr3+-doped yttrium aluminum garnet through co-substitution. The generally hard to achieve long-lasting PersL at the high-energy spectral end is expected to play an irreplaceable role in outdoor long-distance self-sustained “solar-blind” imaging and other UV-triggered applications towards persistent sterilization and photocatalysis.

YAG : R3+ (R = Ce, Dy, Yb) nanophosphor-based luminescent fibre-optic sensors for temperature measurements in the range 20 – 500 °C

We report the development of a group of luminescent fibre-optic temperature sensors that use Ce3+-, Dy3+-, and Yb3+- doped yttrium aluminium garnet (YAG) nanophosphors as thermosensitive materials. The nanophosphors have been prepared in the form of powders with a crystallite size from 19 to 27 nm by a polymer – salt method and exhibit bright luminescence at 550 (YAG : Ce3+), 400, 480 (YAG : Dy3+), and 1030 nm (YAG : Yb3+). The sensor design includes a silica capillary, partially filled with a nanophosphor, and two large-aperture multimode optical fibres located in the capillary, which deliver excitation light and receive and transmit the photoluminescence signal. The photoluminescence signal amplitude of all the sensors decreases exponentially with increasing temperature, pointing to characteristic thermal quenching of photoluminescence and adequate operation of the devices up to 500 °C. The highest temperature sensitivity among the fibre-optic sensors is offered by the YAG : Ce3+ nanophosphor-based devices.

Retinal arterial macroaneurysm in a patient with arterial hypertension

Purpose: To present a case of retinal arterial macroaneurysm in a 48–year–old male patient with systemic arterial hypertension.&#x0D; Case report: A 48–year–old male was admitted to our department because of progressive deterioration of visual acuity in his right eye. He reported diplopia and blurred central field vision. The patient was treated for systemic arterial hypertension and had no other known medical problems. Medical treatment, examination results, and therapy were presented in this case report.&#x0D; Conclusions: In the treatment of patients with retinal arterial macroaneurysm a holistic approach is important. In an attempt to optimize the final outcome of the patient's treatment, both the ocular symptoms and systemic risk factors should be treated. Therapeutic interventions for eyes with retinal arterial macroaneurysm include laser photocoagulation, pneumatic displacement of haemorrhage, vitreoretinal surgical techniques, the use of neodymium–doped yttrium aluminium garnet or argon laser, and intravitreal injections of anti–vascular endothelial growth factor drugs. Their precise roles should be evaluated in further studies.

Investigation of brightness and decay characteristics of YAG:Ce3+, Ca-α-Sialon:Eu2+ and CaAl12O19:Mn4+ phosphors incorporated with Ni-doped SnO2 particles

In this study, we investigated the enhancement in the optical and decay properties of three phosphors, Ce3+-doped yttrium aluminium garnet (YAG:Ce3+), Eu2+-doped yellow oxynitride phosphor (Ca-α-SiAlON:Eu2+), Mn4+-doped aluminate-based phosphor (CaAl12O19:Mn4+), as a result of the interactions of the light-harvesting Ni-doped SnO2 additive. When the YAG:Ce3+ encapsulated in the presence of the nanoscale metal oxide in ethyl cellulose (EC) thin film, exhibited a 59% increase in its brightness as against its non-additive form. Similarly, when excited by 466 nm, the individual blends of Ca-α-SiAlON:Eu2+ and CaAl12O19:Mn4+ phosphors with Ni-doped SnO2 particles demonstrated 65% and 93% improvement in the intensity values, respectively. Decay characteristics of the phosphors and their Ni-doped SnO2 blends were measured in microsecond and nanosecond time scales. When they are in close proximity in a polymeric matrix, the emission- and lifetime-based results have approved that Ni-doped SnO2 particles and phosphors act as donor and acceptor, respectively. Furthermore, the thermal stabilities, quantum efficiencies and CIE chromaticity coordinates of all phosphors and their blends with Ni-doped SnO2 additive were investigated. In parallel with the increase in emission-based intensities and decay time kinetics, we enhanced the internal quantum efficiencies to 94.1%, 86.2% and 80.4%, with the blending of Ni-doped SnO2 particles to YAG:Ce3+, Ca-α-SiAlON:Eu2+, and CaAl12O19:Mn4+ phosphors, respectively. Notably, all of the phosphor composites along with additive indicated higher thermal stability in the temperature range of 303–503 K with respect to the additive-free forms. In the light of these results, the proposed composites can bring a new approach for the existing problems of yellow, orange, and red phosphors concerning the brightness and color rendering index and can be considered as potential candidates on LED technologies.