Doped Yttrium Research Articles

Microwave-assisted combustion synthesis and characterization studies of novel dysprosium doped yttrium calcium borate (Dy3+: Y2CaB10O19) phosphor materials for efficient white light applications

Micro-wave assisted combustion synthesis technique was adopted to synthesize the dysprosium-doped yttrium calcium borate xDy3+: Y(2-x) CaB10O19 (Dy:YCB) polycrystalline phosphor materials with varying concentrations (x = 1, 3, 5, 7 and 9 mol %) for the first time. The formation of phase, crystal structure was analyzed by x-ray diffraction study and was affirmed to be formed pertaining to the monoclinic crystal structure (a = 11.475 Å, b = 6.345 Å, c = 9.223 Å and α = γ = 90°, β = 91.83°) with C2 space group. The absorption capability of the prepared samples was investigated by UV-DRS spectroscopy and the optical band gap was found to be 5.28 eV. FTIR study validated the presence of functional groups and their molecular vibrations. The excitation wavelength of the synthesized samples was found to be 350 nm from photoluminescence excitation (PLE) spectra. The PL emission spectra were recorded to authenticate the emission wavelengths and found to possess two emission peaks at 480 nm (blue) and 577 nm (yellow) contributed by the Dy3+ ions. The optimized dopant concentration of dysprosium ion was fixed at x = 0.07 to avoid the concentration quenching effect. The chromaticity co-ordinate of optimized sample was determined to be x = 0.3188, y = 0.3233 which are closer to ideal white light co-ordinate. The color temperature was determined to be 6209 K, which occurs in the cool white light region. Luminous efficacy of radiation (LER) was determined to be 269.31 l m/Wopt for the optimal phosphor. The luminous efficiency for the optimal phosphor was determined to be 40%. Color rendering index (CRI) of the optimal sample was evaluated to be 77. Internal quantum yield (IQE) of the optimal sample was determined to be 50.58 %. The phosphor materials have excellent thermal stability as validated from the temperature dependent PL measurements.

Modification of structural, morphological, and dielectric properties of barium calcium titanate ceramics with yttrium addition

Barium calcium titanate (BCT) ceramics with varying yttrium doping concentrations were fabricated using the solid-state compaction process to explore the attributes of dopants. (Ba0.75Ca0.25) TiO3 and (Ba0.75Ca0.25) (YyTi(1-y)) O3 where, y = 0.00, 0.10, 0.15, and 0.20 ceramics were synthesized by pressing isostatically in pellet press apparatus, then sintered at 1250 °C with consequent cooling in furnace ambient. The structural, morphological, and dielectric properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and impedance spectroscopy interpretations, respectively. The XRD analysis revealed that the cubic BCT lattice was transformed into a tetragonal structure with Yttrium doping. Scanning electron microscopy (SEM) disclosed that yttrium doping countered the liquid phase formation of BCT as well as influenced grain development and microstructure, leading to the formation of distinct grain boundaries and improved densification. The average grain size (18–29 nm) of the Y-BCT increases as the doping level rises. At 60 Hz, it was reported that the dielectric constant obtained a maximum value of 70000 with a resistivity of 5 × 108 Ώ-cm for y = 0.15. The manifestation of the secondary phase confirmed from XRD, allocating an easy path for oxygen migration, might be responsible for the rise in oxygen vacancy, higher leakage current, and dielectric loss for y = 0.01. Co-doping of calcium and yttrium in BCT ceramics has modified the basic structure and ameliorated composites' structural stability and dielectric characteristics. The optimized sample, upon demonstrating outstanding efficiency, ought to be employed for specific uses such as energy storage devices and capacitors.

Decreasing of Magnetic Saturation of Yttrium Doped Cobalt Ferrite Prepared by the Sol-Gel Auto-Combustion

In this research, a nano-sized cobalt ferrite material doped with Yttrium has been successfully fabricated using the sol-gel method of automatic combustion with variations in low sintering temperatures of 200, 300 and 400 °C. The results of refinement of XRD data using the Rietveld method show that the Yttrium-doped cobalt ferrite compound with a Yttrium concentration molarity of 0.1 possess a cubic crystal system and Fd-3m space group. The increasing annealing temperatures also increase the crystallite size of Yttrium-doped cobalt ferrite with the highest magnitude of 16.05 nm. The FTIR results of the samples indicated the presence of Co-O bonds around wave number 385 cm−1 and Fe-O bonds around wave number 582 cm−1 which are characteristic of the presence of cobalt ferrite compounds. From the VSM measurement results, it can be seen that there is a decrease in magnetic saturation with an increase in annealing temperature. The presence of Yttrium substitution, which takes the place of Fe3+ in cobalt ferrite material, indicates lower saturation magnetization. Image from SEM results showed samples have nanoparticle crystallite size. Evaluation of potential photocatalyst applications using a UV-Visible Spectrophotometer (UV-Vis). For Yttrium doped cobalt ferrite at 200 °C, the best degradation efficiency of Congo Red findings showed a magnitude of 76.10 %; the results are confirmed by the occurrence of the smallest crystallite size (15.11 nm). HIGHLIGHTS Preparation of yttrium-doped cobalt ferrite by the sol-gel auto-combustion method with various annealing temperatures The presence of Yttrium substitution, which takes the place of Fe3+ in cobalt ferrite material, indicates lower saturation magnetization Yttrium-doped cobalt is applied for photocatalytic Congo Red dye in water with the best performance according to the smallest crystallite size GRAPHICAL ABSTRACT

Structural and electrocaloric properties of Yttrium modified Bi0.35Na0.35Sr0.3TiO3 composite

This communication presents the effect of Yttrium and Strontium doping on structural and electrocaloric characteristics of Bismuth Sodium Titanate. Bi0.25Na0.35Sr0.3Y0.1TiO3 electroceramics was synthesized by traditional solid-state mixed-oxide technique. The crystallographic phase formation was confirmed using the X-ray diffraction technique. Rietveld refinement was carried out to extract the unit cell parameters. Average particle size was estimated from the full-width half maxima of the strong XRD peak using Debye-Scherrer’s equation. The temperature dependence of the maximum polarization obtained from P-E loops, the electrocaloric ability of the BNSYT is estimated by calculating the change in the entropy at a field of 6 kV/cm using the standard thermodynamics relation.

Yttrium doping stabilizes the structure of Ni3(NO3)2(OH)4 cathodes for application in advanced Ni-Zn batteries.

Ni3(NO3)2(OH)4 has a high theoretical specific capacitance, low cost, and environmental friendliness, making it a promising electrode material. Specifically, Ni3(NO3)2(OH)4 electrodes have a larger layer spacing (c = 6.898 Å) than Ni(OH)2 electrodes since NO3- has a much larger ionic radius than OH-. The larger layer spacing stores more electrolyte ions, significantly improving the electrochemical activity of the electrodes. Additionally, the interlayer NO3- can enhance the structural stability of Ni3(NO3)2(OH)4. However, since Ni3(NO3)2(OH)4 has a higher molar mass than Ni(OH)2, it has a lower theoretical specific capacity. Consequently, Ni3(NO3)2(OH)4 has not been used in zinc-based alkaline batteries. Studies showed that doping could enhance the electrochemical performance of electrode materials. Therefore, this study used a simple solvothermal reaction to synthesize yttrium-doped Ni3(NO3)2(OH)4 (Y-Ni3(NO3)2(OH)4), assembling a Y-Ni3(NO3)2(OH)4//Zn battery for electrochemical testing. Y-Ni3(NO3)2(OH)4 served as the cathode in the battery. The analysis of Y-Ni3(NO3)2(OH)4 showed that yttrium (Y) doping increased the specific surface area and pore size of Ni3(NO3)2(OH)4 significantly. The increased specific surface area improved the active material utilization, and the abundant mesopores facilitated OH- transport, substantially enhancing the battery's specific capacity and energy density. Ultimately, the specific discharge capacity of the advanced Y-Ni3(NO3)2(OH)4//Zn battery reached 177.97 mA h g-1 at a current density of 4 A g-1, nearly doubling the capacity of the earlier Ni3(NO3)2(OH)4//Zn battery (103.59 mA h g-1).

Effects of yttrium doping on high-temperature oxidation, friction, and wear properties of CrAlN films

This study investigates the deposition of CrAlYN nanomultilayer films with different yttrium (Y) contents on M2 tool steel and single-crystal Si wafer using unbalanced magnetron-sputtering ion-plating technology. Transmission and scanning electron microscopic and scanning morphologies, x-ray diffraction pattern, energy dispersive spectra, nanoindentation, high-temperature oxidation, and high-temperature tribological analyses show that CrAlYN nanomultilayer films have a face-centered cubic (fcc) crystal structure with a modulation period of CrN/YN+AlN/CrN/AlN. CrAlYN films exhibit optimal mechanical performance when Y content is 1.13at%. However, a substantial drop occurs when Y content increases to 2.67at%. As Y content increases, the high-temperature oxidation resistance, friction, and wear of CrAlYN films first increase and then decrease. Notably, films with the Y content of 1.13at% have optimal resistance to high-temperature oxidation, friction, and wear.

Mitigating irreversible phase transition of Y-doped LiNi0.925Co0.03Mn0.045O2 by lattice engineering

The commercialization of ternary layered cathode materials with a relative nickel content of more than 90 % faces serious challenges. Among them, it is urgent to address the issues of rapid capacity degradation and structural degradation. Herein, we provide a simple process for doping yttrium at the precursor preparation stage. The feasibility of yttrium doping in the precursor and the positive effects of yttrium ions on the crystal structure and properties of the cathode materials are scientifically explained by a variety of characterization and testing methods, such as Eh-pH, Particle Size Analyzer, ICP, SEM, EDS, XRD, XPS, HRTEM, dQ/dV, CV, EIS and DFT. Yttrium-doped NCMY cathode materials have more stable lattice oxygen and significantly less irreversible phase transition. Furthermore, the electrochemical performance of the NCMY cathode material is significantly improved, with a capacity retention rate of 82.71 % after 150 cycles at a current density of 1C, which is much higher than 65.39 % for NCM. The NCMY cathode material significantly improves the lithium ion diffusion ability, especially at the high rate of 10C, the discharge specific capacity is still as high as 177.05 mAh g−1.

Effect of Yttrium doping on antibacterial and antioxidant property of LaTiO3

The advancement of multidrug-resistant bacterial strains and their adverse effects is one of the most significant global health issues. The perovskite nanomaterial with combined antioxidant and antibacterial activities in one molecule has the potential for improved therapeutic solutions. In this work, Yttrium-doped Lanthanum Titanate (LaTi1 −xYxO3, where x = 0, 0.05, and 0.1) was synthesized using auto combustion technique. Excellent crystalline structure with a tetragonal system is revealed by X-ray diffraction analysis (XRD). UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), Fourier transform infrared (FTIR), and photoluminescence (PL) were used to study its optical characteristics. The field emission scanning electron microscope (FE-SEM) shows rod-like pellet-shaped Yttrium-doped nanostructures, and the elements present were confirmed with the Energy Dispersive X-Ray Analysis (EDAX). Various concentrations of the synthesized materials were tested for antibacterial activity against Gram-positive (Staphylococcus aureus 902) and Gram-negative (E. coli 443) strains using the agar-well diffusion method with gentamicin antibiotic as a positive control. High antibacterial activity of 87.1% and 83.3% was shown by 10% Yttrium-doped LaTiO3 (LY(0.1)TO) at 500 mg/mL against both positive and negative stains, respectively. Moreover, the antioxidant properties of synthesized materials were assessed with IC50 values of 352.33 µg/mL, 458.055 µg/mL, and 440.163 µg/mL for samples LaTi1 − xYxO3, where x = 0, 0.05, and 0.1 respectively. The antibacterial and antioxidant capabilities of the proposed samples illustrate their applicability in various biomedical applications.

Investigating Fe-doped yttrium oxide nanophosphors for enhanced latent fingerprint visualization and deep learning analysis

In the study, synthesized Fe3+ doped yttrium oxide nanophosphors (Y2O3:Fe NPs, 1–11 mol%), including structural, microstructural, chemical state, optical, thermal, and photoluminescence properties, are extensively studied. An optimized 7 mol % Fe doped Y2O3 NPs powder is used to develop latent fingerprints on various surfaces through a simple powder dusting method. The developed fingerprints are visible under 254 nm UV light. The research also analyzes several pore properties: size, shape, number, position, type, and inter-distance. A fingerprint recognition deep learning model based on the YoLOv8 algorithm was developed and employed for analyzing both single and overlapped fingerprints. These highly effective NPs are also used to create a transparent anti-counterfeiting (AC) ink that exhibits AC properties when exposed to UV light, and their physical and chemical stability opens novel applications in the AC field. The optimized Y2O3:7Fe3+ NPs are an excellent luminous platform for solid-state lighting, AC, and dermatoglyphics applications.

Structural and dielectric properties of Y3+ doped SrTiO3: a novel anode materials for solid oxide fuel cell

An ongoing and elusive task is to create single phase anode materials for solid oxide fuel cells (SOFC). Compared to the typical Ni-YSZ cermet anode, perovskite oxide based anode material has a number of benefits. Here, we present the structural and electrical characteristics of Y3+ doped SrTiO3 ceramics that are used as the anode in solid oxide fuel cells. The samples with nominal composition x = 0 and 0.05 were synthesized by high energy ball milling. The powder X-ray diffraction pattern reveals that the synthesized samples crystallize into cubic crystal structure with space group Pm3m for both the compositions. The samples were sintered at a temperature of 1300 °C for 6h. The sintered density of the samples was found to be greater than 97%. The temperature dependent dielectric measurement studies reveal that dielectric constant increases with yttrium doping and shows relaxer behavior. A higher dielectric constant and electrical conductivity was observed for the Y-doped sample which fulfill the basic requirement for anode materials of solid oxide fuel cells.

Improvement in the structural, magnetic and electromagnetic behaviour of barium hexaferrites with yttrium doping for EMI shielding

Electromagnetic interference (EMI) shielding is critical for protecting electronic devices from interference generated by various sources such as power lines, radio waves, microwaves, and electronic devices. In this current study, we present a thorough investigation of the structural, magnetic, and electromagnetic properties of Y3+ doped M-type barium nano hexaferrites. Polycrystalline BaFe12−xYxO19 (x = 0.0, 0.3, 0.5, 0.7, and 0.9) hexaferrites are prepared using the citrate precursor method. The results of X-ray diffraction (XRD), Rietveld refinement and Raman spectroscopy confirmed that all samples have a single-phase, and pure hexagonal crystalline structure with space group P69/mmc. This result is consistent for all the prepared compositions. The structure and dopant materials in different chemical states of the sample are determined based on the X-ray photoelectron spectroscopy (XPS) spectrum. Field emission scanning electron microscopy (FESEM) analysis showed that the particles had a distinct hexagonal morphology. The chemical composition of the prepared hexaferrites is investigated using energy dispersive X-ray analysis (EDAX). UV spectroscopy showed an inverse relationship between the molar ratio of yttrium and the band gap. Vibrating sample magnetometer (VSM) results showed a decrease in saturation magnetization (Ms) and coercivity (Hc) with increasing fraction of yttrium ions. The shielding efficiency (SE) of the synthesized hexa materials against EMI is evaluated using a vector network analyser (VNA). In particular, effective EMI shielding was observed in the frequency spectra of 8–12 GHz (X-band region). Among the tested compositions, BaFe12–0.7Y0.7O19 with a thickness of 3 mm exhibited highest SE of 80.07 dB in the X-band region. The proposed yttrium-substituted barium M-type hexagonal ferrites exhibit significant reflection loss with enhanced absorption spectrum even when applied to an extremely thin 3 mm material, making it a possible preference as the radar-absorbed compound for EMI attenuators for weather monitoring, radar tracking, air traffic management, and gigahertz antennas. Furthermore, commercial applications including long-term magnetic media for recording, storing information, etc. are possible uses of the synthesised magnetic yttrium-doped barium M-type hexagonal ferrites.

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.

The effect of terbium on the optical dispersion and magneto-optical properties of YIG crystals grown by flux-Bridgman method

R3Fe5O12 (RIG) crystals are the key elements for magneto-optical isolators in the near-infrared (NIR) to mid-infrared (MIR) region, with ever-growing demands for integrated photonics. However, the growth of high-quality single crystals is still a big obstacle. The effect of rare earths on the optical and magneto-optical properties of YIG crystals is not well understood. Herein, a series of high quality Tb3+ doped yttrium iron garnet (Y3-xTbxFe5O12, x = 0, 0.5, 1.0, 1.5, 3.0) crystals have been successfully obtained by the flux-Bridgman method, with sizes over 20 mm. Tb:YIG crystals reserve typical cubic garnet structure, with spatial group of Ia3d. The lattice constants increase from 12.377 Å (YIG) to 12.448 Å (TbIG). The refractive index decreases from 2.38 (500 nm) to 2.11 (2500 nm) for YIG crystal, and it reduces from 2.51 (500 nm) to 2.17 (2500 nm) for TbIG crystal. The optical dispersion of the refractive indices was well fitted by the Wemple and DiDomenico (WDD) and the Sellmeier models, respectively. Relatively lower values of the absorption coefficient of the Tb:YIG crystals confirm the high transparency in the NIR region. The characteristic absorption of Tb3+ was observed from 1700 nm to 2500 nm. The specific Faraday rotation angles (θF) of both YIG and TbIG decrease with increasing wavelength, reaching 235.4 and 366.5 °/cm at 1300 nm, respectively. Compared with that of YIG, θF of TbIG crystal shows stronger wavelength dependence. This work provides more insight into the role of rare earths on the optical and magneto-optical behavior of RIG crystals, which will accelerate the design of high-performance magneto-optical crystals for application in NIR-MIR wavelength.

Effect of yttrium doping on the photocatalytic properties of ZnO thin films

Zinc oxide films with different levels of yttrium doping are deposited on glass substrates, using radio-frequency magnetron sputtering. Photocatalytic properties were investigated for such Y-doping weight concentration: 0, 2.4, 3.9, 4.7 wt. %. The studies showed that the Y-doping significantly improves the photocatalytic activity of the ZnO thin films. It was shown that the ZnO:Y 3.9 wt. % presents the highest degradation efficiency of 100 % during 80 minutes and the largest rate constant 9.6 · 10-2 min-1 among all samples.

Spectroscopic investigations and Judd-Ofelt analysis of Sm3+ doped Y2O3 transparent ceramics

Sm3+ doped yttria transparent ceramics (SmxY1-x)2O3 (x = 0.01, 0.015, 0.03) were fabricated by Spark Plasma Sintering method. Absorption spectra, as well as emission spectra and luminescence lifetime were carried out at room temperature. Judd-Ofelt (J-O) theory was used to calculate the Ωt (t = 2, 4, 6) intensity parameters. The spontaneous transition probabilities, radiative lifetime, branching ratio, and stimulated emission cross-sections have been calculated for 4G5/2 excited level. The emission cross section for the 4G5/2 → 6H7/2 transition at about 607 nm was calculated to be 6.73 × 10−22 cm2. The results indicate that Sm:Y2O3 ceramic may be a potential reddish orange-light laser material around 607 nm.

Study of radiation shielding and luminescence properties of 1.5 µm emission from Er3+ doped zinc yttrium borate glasses

Every year, a new material composition composed of various oxides glasses emerges, and researchers investigate fascinating properties because of which they contribute more scientific evidence to tailor their properties to enhance its technological importance in solid-state device applications. In purview of such contribution the present work provide a new material composed of (50-x)B2O3 + 45ZnO+ 5Y2O3 + xEr2O3 where (x = 0.0, 0.1, 0.25, 0.5, 1.0) glasses which were prepared with and without yttrium (x = 0.0, 0.1, 0.25, 0.5, 1.0) content. To determine their suitability, various physical, optical, and radiation shielding tests were performed on the synthesized glasses. In this perspective, we highlight some aspects of the prepared glasses, density of the glasses increases with increasing concentration of high ‘z′ oxides, interestingly non-bridging oxygen’s increases and bandgap decreases when erbium content introduced in the matrix. The oscillator strength was evaluated for the observed eight transitions for the present glasses and found to be within the limits as per the root mean square fitting. The Judd-Ofelt theory was used to estimate the Er3+ ions' spectral transition, and the trend (Ω6 > Ω2 > Ω4) for the current glasses indicates that the ligands and Er3+ ions have weak bonds with one another. The lifetime τexp of 4I13/2 transition shows an increase in its value from 112 μs to 238 μs for 0.5 mol% and 1.0 mol% Er2O3 concentration respectively. At 1.5 µm, the 4I13/2 → 4I15/2 transition-related photoemission band is notable because it is useful for IR laser applications. The optical gain co-efficient of the prepared glasses was investigated using the absorption gain cross-section, emission cross-section, and optical gain cross-section. The near-infrared absorption and emission reveal their role in IR device applications. Radiation shielding properties like the mass attenuation coefficient ((µm), effective electron density (Neff), and effective atomic numbers (Zeff) are critical system of measurements for evaluating transparent material shielding performance.

High-Temperature Oxidation Behaviors of AlCrTiSi0.2 High-Entropy Alloy Doped with Rare Earth La and Y

High-entropy alloys (HEAs) were prepared with strong antioxidant metals Al, Cr, Ti, and Si as matrix elements, and the effects of rare earth (RE) lanthanum (La) and yttrium (Y) doping on their microstructures and high-temperature oxidation resistance were explored in this study. The AlCrTiSi0.2RE0.02 HEAs were prepared by using vacuum arc melting and were oxidized mass gain at 1000 °C. After oxidation for 53 h, AlCrTiSi0.2 HEA had a mass increase of 1.195 mg/cm2, and it had the best oxidation resistance of three HEAs (AlCrTiSi0.2, AlCrTiSi0.2La0.02, and AlCrTiSi0.2Y0.02). The surface oxide layers of three HEAs mainly consisted of Al and Ti oxides; the layered oxide film of AlCrTiSi0.2 alloy was mainly composed of dense Al2O3, and the acicular oxide films of AlCrTiSi0.2La0.02 and AlCrTiSi0.2Y0.02 alloys were primarily composed of loose Ti oxide. Doping La and Y decreased the oxidation resistance of AlCrTiSi0.2. In the early stage of oxidation of rare earth HEAs, the surface oxide layer was loose because La and Y reacted with the matrix metal, which slowed down the diffusion of element Al or accelerated the diffusion of element Ti. In the late stage of oxidation, La and Y interacted with O and entered the matrix metal to form rare earth oxides.

Yttrium Doping Effects on Ferroelectricity and Electric Properties of As-Deposited Hf1-xZrxO2 Thin Films via Atomic Layer Deposition.

Hf1-xZrxO2 (HZO) thin films are versatile materials suitable for advanced ferroelectric semiconductor devices. Previous studies have shown that the ferroelectricity of HZO thin films can be stabilized by doping them with group III elements at low concentrations. While doping with Y improves the ferroelectric properties, there has been limited research on Y-HZO thin films fabricated using atomic layer deposition (ALD). In this study, we investigated the effects of Y-doping cycles on the ferroelectric and electrical properties of as-deposited Y-HZO thin films with varying compositions fabricated through ALD. The Y-HZO thin films were stably crystallized without the need for post-thermal treatment and exhibited transition behavior depending on the Y-doping cycle and initial composition ratio of the HZO thin films. These Y-HZO thin films offer several advantages, including enhanced dielectric constant, leakage current density, and improved endurance. Moreover, the optimized Y-doping cycle induced a phase transformation that resulted in Y-HZO thin films with improved ferroelectric properties, exhibiting stable behavior without fatigue for up to 1010 cycles. These as-deposited Y-HZO thin films show promise for applications in semiconductor devices that require high ferroelectric properties, excellent electrical properties, and reliable performance with a low thermal budget.

Growth, optical dispersion and magnetic behavior of Dy3+ doped yttrium iron garnet crystals

Y3Fe5O12 (YIG) crystals are highly desirable for the fabrication of mid-infrared isolators with the rapid growth of optical communications, although it is rather challenging to grow large size and high-quality single crystals. Dy3+ doping is expected to improve the optical and magneto-optical properties. However, high quality Dy:YIG crystals and the adjustment of Dy3+ on the structure and optical behavior of YIG crystal remain unclear, impeding its practical applications. Herein, a series of Y3–xDyxFe5O12 (x = 0, 0.5, 1.0, 1.5, 3) solid solution crystals was grown by the flux-Bridgman method and single crystals up to 25 mm were obtained. With the introduction of Dy3+, lattice parameters are gradually enlarged from 1.2379 nm (YIG) to 1.2420 nm (DyIG). Typical Dy3+ absorption peaks are observed around 1070, 1265 and 1670 nm. The refractive index decreases from 2.37 (500 nm) to 2.10 (2500 nm) for YIG crystal, and it reduces from 2.47 (500 nm) to 2.16 (2500 nm) for DyIG crystal. The optical bandgaps remain almost unchanged for Dy:YIG crystals. The optical dispersion of the refractive indices was finely fitted by the Wemple and DiDomenico (WDD) and the Sellmeier models, respectively. With the increase of Dy3+ content, the saturation magnetization (Ms) decreases significantly from 23.62 emu/g (YIG) to 5.33 emu/g (DyIG). Small coercive field is persisted for this system, endowing small external magnetic field. These results provide valuable references for the manipulation of rare earths on the properties of magneto-optical crystals, which is beneficial to the design of high-performance garnet crystals for the application of optical switching and non-reciprocal related devices.

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).