Doped Y3Al5O12 Research Articles

Photoluminescence and Raman spectroscopy of Ce3+ doped Y3Al5O12 single crystalline films grown onto Y3Al5O12 and Lu3Al5O12 substrates

Raman spectroscopy, high spectral resolution luminescence, and X-ray diffraction techniques were employed to study two Ce3+ doped Y3Al5O12 single crystalline films grown by liquid phase epitaxy method onto Y3Al5O12 and Lu3Al5O12 single crystal substrates. Optical spectra were obtained with a micrometer step along the cross-sections of epitaxial structures, allowing excellent differentiation of the film, the transition layer, and the substrate of each sample. X-ray measurements demonstrate the mismatch between the lattice constants of the Y3Al5O12:Ce3+ film and its Lu3Al5O12 substrate, an effect related to different compositions. Consequently, the film grown onto Lu3Al5O12 exhibits higher residual stresses than its counterpart grown onto Y3Al5O12. This was confirmed by a mutual comparison of the Raman bands positions of the films. The luminescence spectra of both samples consist mainly of cerium 5d-4f emission, the intensity of which allows for additional study of epitaxial cross section and estimation of the size of transition layer.

High-efficiency Ho:YAG single-crystal fiber laser in-band pumped by a 1.9 μm laser diode

We report on a 10-watt-level, efficient 2 μm Ho:YAG (0.6 at.% Ho3+ doped Y3Al5O12) single crystal fiber (SCF) laser in-band pumped by a 1.9 μm laser diode. Benefiting from the high gain of the SCF and the unique propagation features of the pump and laser beams, a maximum output power of 10.77 W is achieved with T OC = 20%, corresponding to a slope efficiency of 61.8%. The higher efficiency of 64.8% and the output power of 9.8 W are obtained with T OC = 50%. Compared to the traditional bulk crystal, wave-guiding of the pump light in the SCF can extend the gain region and thus improve the laser efficiency, which provides a simple and effective method to improve the utilization rate of the pump light even for the low-brightness laser diodes.

Sustainable inorganic pigments with high near-infra-red reflectance based on Fe3+ doped YAlO3 for high temperature applications

Non-toxic inorganic pigments based on the Fe(III)-doped YAlO3 with high near-infra-red (NIR) reflectance were synthesized by a modified Pechini method at 1200 °C. A complete solid solution in the YAl1−xFexO3 system (0 ≤x ≤ 1) was prepared, yielding a wide range of colourations from yellow to red, depending on the iron content.Good pigment stability was achieved in a commercial high temperature glaze, used in the ceramic industry to colour glazes on tiles. The pieces coated with the pigmented glazes reached NIR solar reflectance values between 43% and 32%. The temperature protection studies carried out with the glazes pigmented with YAl0.75Fe0.25O3 and YFeO3 compositions, conclude that the pigmented samples reduce the temperature of a building by 5 °C and 4 °C, respectively, in comparison to the unpigmented glaze.Thus, these pigments can be excellent candidates for used in high-temperature applications such as colouring ceramic high temperatures glazes, as well as cool pigments in walls or roofs of buildings.

Influence of Er3+ doping on the mechanical and thermophysical properties of (ErxY1-x)3Al5O12 ceramics

In this work, Er3+ was selected to replace Y3+ in the yttrium aluminium garnet (YAG) in order to improve its mechanical and thermophysical properties. A series of (ErxY1-x)3Al5O12 (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) ceramics were prepared by solid-state synthesis method at 1000 ?C and finally sintered at 1600 ?C for 5 h. The microstructure and morphology of the prepared ceramics were investigated. The results showed that all Er3+ doped Y3Al5O12 ceramics exhibited single garnet-type YAG phase and good compactness. With the increase of Er3+ doping concentration, the thermal conductivity of the (ErxY1-x)3Al5O12 ceramics decreased slowly and then increased subsequently. Among the investigated specimens, the (Er0.7Y0.3)3Al5O12 had the lowest thermal conductivity (1.51W/m?K, at 1000 ?C), which was about 28% lower than that of the pure YAG (2.1W/m?K, at 1000 ?C). As the Er3+ doping concentration increased, the thermal expansion coefficient of the (ErxY1-x)3Al5O12 ceramics hardly changed, remaining around 9.08 ? 10?6 K?1 at 1200 ?C. Moreover, when the Er3+ doping concentration exceeded 0.5, the mechanical properties of the (ErxY1-x)3Al5O12 ceramics increased suddenly. Specifically, the hardness increased from 14.28 to 16.53GPa and the bending strength increased from 231.74 to 324.49MPa.

Effect of extra added Mg2+ and Si4+ on the microstructure and luminescence properties of Ce:YAG ceramic phosphors for high power LED/LD lighting

The study deals with the use of different amounts of MgO or tetraethyl orthosilicate (C8H20O4Si, TEOS), from 0.04 wt %, 0.06 wt %, 0.08 wt %, 0.4 wt %, 0.6 wt % to 0.8 wt %, respectively, as additional sintering aids during the vacuum sintering of transparent Ce3+ doped Y3Al5O12 (Ce:YAG) ceramics to investigate their effect on microstructure and luminescence properties. A comparative study was carried out by using X - ray diffraction, scanning electron microscopy/energy dispersive X - ray spectroscopy, optical and photo-luminesce spectra, as well as electroluminescent spectra. The dominant garnet phase was obtained even when adding 0.8 wt % of MgO or TEOS, while adding MgO led to finer average grain size (∼ 5 - 10 μm) and more homogenous distribution compared to TEOS (∼ 20 - 25 μm) in Ce:YAG ceramics. Adding a large amount of MgO was found to result in the segregation of MgO in Ce:YAG ceramics, while an excess of TEOS led to the segregation of Al2O3. A strong absorption peak at 308 nm was observed in Ce:YAG ceramics with MgO sintering aids, which was ascribed to the existence of Ce4+ induced by a charge compensation effect of Mg2+. The optimum transmittance reached 80% @ 800 nm in Ce:YAG ceramics when adding 0.6 wt % TEOS, which also exhibited a maximum luminous efficacy of 106 lm/W. Si4+ was experimentally proved to have a better optimization effect on luminous efficacy compared to Mg2+.

Basic Characteristics of Dose Distributions of Photons Beam for Radiotherapeutic Applications Using YAG:Ce Crystal Detectors.

Thermostimulated luminescence (TSL) dosimetry is a versatile tool for the assessment of dose from ionizing radiation. In this work, the Ce3+ doped Y3Al5O12 garnet (YAG:Ce) with a density ρ = 4.56 g/cm3 and effective atomic number Zeff = 35 emerged as a prospective TSL material in radiotherapy applications due to its excellent radiation stability, uniformity of structural and optical properties, high yield of TSL, and good position of main glow peak around 290-300 °C. Namely, the set of TSL detectors produced from the YAG:Ce single crystal is used for identification of the uniformity of dose and energy spectra of X-ray radiation generated by the clinical accelerator with 6 MV and 15 MV beams located in Radiotherapy Department at the Oncology Center in Bydgoszcz, Poland. We have found that the YAG:Ce crystal detects shows very promising results for registration of X-ray radiation generated by the accelerator with 6 MV beam. The next step in the research is connected with application of TSL detectors based on the crystals of much heavier garnets than YAG. It is estimated that the LuAG:Ce garnet crystals with high density ρ = 6.0 g/cm3 and Zeff = 62 can be used to evaluate the X-rays produced by the accelerator with the 15 MV beam.

Crystal configuration, spectroscopic and optical characteristics of Er3+ doped YAlO3 perovskites for advanced photonic appliances

Perovskite structural based Er (III) doped YAlO3 nanophosphors have been synthesized via cost-effective and simplistic urea assisted solution combustion (SC) synthetic route. The resulting products are well characterized by various structural and spectroscopic studies in detailed. Crystal structure has been elucidated by X-ray diffraction (XRD) and Rietveld refinement method. Prepared powdered samples are crystallized in orthorhombic crystal system having space group Pbnm (62). Energy dispersive X-ray (EDX) spectroscopic analysis is performed to evaluate the atomic (%) and weight (%) of constitute elements and their relative distribution through mapping profile. The most intense excitation peak centred at 378 nm is well harmonized with the distinctive wavelength of commercialized NUV based LED chips. Photoluminescence (PL) studies depicted green emissions of doped nanophosphors upon excitation at 378 nm wavelength. The most intense emission peak at 549 nm is accredited to 4S3/2 →4I15/2 electronic transition of the Er3+ ion. Moreover, PL data is exploited to obtain photometric parameters viz. color coordinates (x and y), color purity (%) and correlated color temperature (CCT), which robustly recommended for their usage as NUV based solid-state advance photonic appliances.

Structural, morphological and optoelectronic aspects of YAlO3:Dy3+ doped nanocrystalline materials for NUV energized WLEDs

Cost-effective urea assisted solution combustion (SC) synthetic method was employed to prepare a series of doped YAlO3:xDy3+ (0.01–0.08 mol) phosphors. The resulting powdered samples were comprehensively examined through various structural as well as optical measurements. Rietveld refinement studies concluded that prepared nanomaterials structured into the orthorhombic system having Pbnm (62) space group. Energy dispersive spectral (EDS) analysis was executed to observe the relative proportions of constituent elements in all doped nanophosphors. Transmission electron microscopy (TEM) micrograph indicated the presence of agglomerated particles with the average size in the nano range. Photoluminescence excitation (PLE) spectra showed that the designated phosphors could be excited by near ultraviolet (NUV) energized lighting sources. The strongest emission centred at 576 nm, corresponding to electric dipole (4F9/2 → 6H13/2) transition of Dy(III) ion. Furthermore, characteristics photometric parameters viz. correlated color temperature (CCT), chromaticity coordinates (x and y), and color purity (%) were figure out with the aid of PL data, which strongly endorsed their usage in NUV energized WLEDs applications.

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.

Modification of spectrum and laser performance on a Tm3+ doped YAlO3 crystal by a specific electron beam radiation

Presented here was the spectrum and laser performance of a Tm:YAP (YAlO3) laser crystal under 1 MeV electron irradiation. It was demonstrated that, under the radiation of S3E15, the absorption spectrum was enhanced of about 1.2 times at the absorption peak at 688 nm, and the absorption peak at 794 nm was enhanced of about 1.16 times, the laser threshold increased from 2.7 W to 2.93 W, the maximum output power reduced from 2.89 W to 2.585 W an d the slope efficiency decreased of nearly 3% at pump power of 13.325 W, the center wavelength drifted from 1991.68 nm to 1992.76 nm, the wavelength FWHM increased by about 0.7 nm.

Spectroscopic properties of Tb:Y3Al5O12 crystal for visible laser application

Tb3+ doped Y3Al5O12 (Tb:YAG) single crystal has been grown by the Czochralski method. Optical spectroscopic characterization of the crystal was performed in order to evaluate the potential for the visible laser application. Based on the Judd–Ofelt theory, the spectroscopic parameters Ωt (t = 2, 3, 6), spontaneous transition probabilities, fluorescence branch ratio and the radiation lifetime of excited state 5D4 state were calculated. The green emission cross section of 5D4→7F5 transition were calculated to be 1.23 × 10−21 cm2, The yellow emission cross section of 5D4→7F4 transition were calculated to be 7.08 × 10−23 cm2. The decay time of the 5D4 level was measured to be 3.12 ms, which is in reasonable agreement with the radiation lifetime of 3.30 ms. All the results indicate the potential of Tb:YAG crystal as a visible laser material.

Effect of grain size on the luminescent properties of Ce3+ doped Y3Al5O12 ceramic phosphor plates

Ceramic phosphor plates of Ce3+ doped Y3Al5O12:Ce (or YAG:Ce) are considered better wavelength converters for high power light emitting diode (LED) and laser diode (LD) lighting applications due to their significantly better thermal conductivity and heat resistance as compared to phosphor powder/epoxy films. Understanding the relationship between the microstructures of YAG:Ce ceramic phosphor plates and their luminescent properties is of importance to optimize their luminescent properties. In this work, we have found that the grain size of Ce3+ doped YAG ceramic phosphor plates has a significant effect on their luminescent properties. Our results show that ceramic phosphor plates with larger grains size can not only convert blue light to yellow light more efficiently, but also have better resistance to thermal quenching. When excited by a blue light source (peak wavelength of 455 nm, optical power of 24.75 W) generated by an LED COB, the ceramic phosphor plate with average grain size of 36 μm is found to have blue-to-yellow light conversion efficiency 46% higher than that of the sample with average grain size of 6 μm (309 lm W−1 vs 213 lm W−1). As they are heated from 300 K to 473 K, their emission intensities decrease by 15%, 19% and 21% for the samples with average grain sizes of 36 μm, 9 μm and 6 μm, respectively.

Molten salt synthesis and luminescence of Dy3+‐doped Y3Al5O12 phosphors

Dy3+ -doped Y3 Al5 O12 phosphors were prepared at a relatively low temperature using molten salt synthesis. The phase of the prepared Dy3+ -doped Y3 Al5 O12 phosphors was confirmed using X-ray powder diffraction. Results indicated that Dy3+ doping did not change the Y3 Al5 O12 phase. Following excitation at 352 nm, emission spectra of the Dy3+ -doped Y3 Al5 O12 phosphors consisted of blue, yellow, and red emission bands. The influence of Dy3+ concentration and excitation wavelength on emission was investigated. The ratio of yellow light to blue light varied with change in Dy3+ doping concentration, due to changes in the structure around Dy3+ . Emission intensities also changed when the excitation wavelength was changed. This variation is luminescence generated a system for tunable white light for Dy3+ -doped Y3 Al5 O12 phosphors.

First-principle study of the microstructure and electronic properties for Cr3+ doped yttrium orthoaluminate

Chromium ion (Cr3+) doped YAlO3 host crystal shows strong prospects for the exploitation of new optical materials. However, the microstructure of Cr3+ doped of YAlO3 is still unclear. In this work, we systematically explore the structural evolutions of Cr3+ doped of YAlO3 system by using the CALYPSO method and density functional theory. A novel cage-like structure with P-1 space group is identified for the first time. The impurity Cr3+ ion can naturally substitute the Al3+ ion of the central site in the crystal lattice. The result show that the impurity Cr3+ concentration is determined to be 6.25%, which is almost comparable to the experiments. The perfect agreement between our simulated X-ray diffraction patterns and the measured ones demonstrates the validity of the ground-state structure. The calculation of electronic band structure for Cr3+ doped YAlO3 reveals a closure of the insulator band gap, forming an energy gap of 2.94 eV. The result of electronic density of states shows that it is the impurity Cr3+ ion that leads to a transition from insulator to semiconductor. By analyzing the electron localization function of Cr3+ doped of YAlO3 crystal, we conclude that the Cr–O interaction is dominantly ionic bond. The obtained results could provide an important understanding of the transition-metal doped host materials.

Processing thin, dense, transparent Ce:Y3Al5O12 films from flame made nanopowders for white light applications

Flame made metal oxide nanopowders enable processing of dense, transparent thin (< 50 μm) films of Ce3+ doped Y3Al5O12 for white light applications. The addition of very small amounts of SiO2 (0.14 wt. %) and the use of a final 95:5 N2:H2 atmosphere sintering step permits nearly complete removal of pores from films originally sintered in O2. Furthermore, the introduction of this final step allows reduction in processing temperatures needed to effect Ce4+ reduction to Ce3+ by several hundred degrees below typical temperatures of >1600 °C. At 20–50 μm, the reported films are also much thinner than previously reported for the same materials normally produced by solid state reactions of micron size powders. Spectrofluorometric measurements of the dense transparent films exhibit excitation spectra centered around 450 nm and broad emission spectra in the 470–750 nm range with two peaks centered at 537 and 570 nm, confirming their applicability as a phosphor for white light emitting diodes.

Composite thermoluminescent detectors based on the Ce3+ doped LuAG/YAG and YAG/LuAG epitaxial structures

This work presents the first results on creation of composite thermoluminescent (TL) detectors based on the film-crystal epitaxial structures of garnet compounds for the simultaneous registration of the mixed ionization fluxes containing α- and β-particles. Two types of TL detectors containing combinations of the single crystalline films (SCFs) and single crystal (SC) substrates of Ce3+ doped Y3Al5O12 (YAG) and Lu3Al5O12 (LuAG) garnets, were considered. The LuAG:Ce SCF/YAG:Ce SC and YAG:Ce SCF/LuAG:Ce SC epitaxial structures were grown by the liquid phase epitaxy (LPE) method from (overcooled) supercooled? melt-solution based on the PbO–B2O3 flux and their thermoluminescent properties were examined under excitation by α- and β-particles of 242Am' and 90Sr –90Y sources. The registration of α- and β-particles was performed using differences between TL glow curves of SCFs and substrates. The first results on separation of TL signals from SCF and SC components for LuAG:Ce SCF/YAG:Ce SC and YAG:Ce SCF/LuAG:Ce SC epitaxial structures under α- and β-excitation are encouraging. This enables consideration of these epitaxial structures as prototypes at the next steps of producing the composite TL detectors based on different oxide materials using the LPE growth method.

Optical and scintillation properties of Nd-doped YAlO3 crystals

Nominally Nd 0.1, 0.5, 1 and 2% doped YAlO3 (YAP) single crystals were synthesized by the floating zone method to evaluate their optical and scintillation properties. In photoluminescence (PL), all the samples showed sharp emission lines in the UV-VIS region, and the PL quantum yield in this spectral range was 5–15%. The PL decay time of the 4F7/2 → 4I9/2 transition was evaluated to be around 150 ms. In scintillation emission spectrum under X-ray irradiation, several emission lines due to the 4f-4f transitions of Nd3+ were observed in the UV-VIS range. These emissions was found to consist of two decay constants of a few μs and 100–150 ms. When irradiated with 662 keV γ-rays from 137Cs, the Nd 0.1% doped sample exhibited the highest scintillation light yield of 12500 ph/MeV determined by pulse height analysis.

Co-precipitation synthesis, structural characterization and fluorescent analysis of Nd3+ doped Y3Al5O12 and Yb3Al5O12 nanocrystallines

Nd3+, as one of the most important rare-earth (RE) ion, has been playing a significant role in pumping the infrared (IR) light. Depending on different synthesis strategies, doping content, and crystal lattice, however, Nd3+ always shows different IR intensity. In this work, we have fabricated two series of Nd3+ doped nanocrystallines that share with the same crystal structure, i.e., Nd3+ doped Y3Al5O12 (YAG) and Yb3Al5O12 (YbAG), through using the co-precipitation synthesis method while the ammonium bicarbonate as the precipitant agent. To reveal the influence of the synthesis conditions (e.g., synthetic temperature and pH value) on structural and florescent properties of Nd3+ doped YAG and YbAG nanocrystallines, several techniques have been performed in this work, including the X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric-differential scanning calorimeter (TG-DSC), Fourier transform infrared (FT-IR) spectroscopy, Raman and florescent spectroscopy spectra. Our results reveal that the optimal synthesis conditions are 1000 °C and pH 8 for YAG:Nd3+ and 900 °C and pH 9 for YbAG:Nd3+. Moreover, we also find the optimal Nd3+ doping contents of the YAG:Nd3+ and YbAG:Nd3+ nanocrystallines are 3% and 1.5%, which correspond to the strongest fluorescent intensity upon excitation at 808 nm and 980 nm, respectively. Typically, we reveal that substitution of Y with Yb ions could allow to enhancing the Nd3+ fluorescent intensity upon excitation at 808 nm. This work provides new insights into designing excellent crystal materials that can allow us to realize the laser transparent ceramics.

Influence of Mg2+/Ga3+ doping on luminescence of Y3Al5O12:Ce3+ phosphors

Mg2+/Ga3+ doped Y3Al5O12:Ce3+ phosphors were synthesized through a solid state reaction. The phase and luminescent of the synthesized phosphors were investigated. For Ga3+ codoped Y2.96Ce0.04Al(5−x)GaxO12 phosphors, the emission intensity increases with the increase of Ga3+ concentration up to Y2.96Ce0.04Al4.80Ga0.20O12 and then decreases with a further increase of Ga3+ concentration, but the emission peak shifts to shorter wavelength continuously in the Ga3+ doping concentration range of 0.05–0.25. For Mg2+/Ga3+ codoped Y2.96Ce0.04Al(4.8−y)Ga0.20MgyO12 phosphors, the emission intensity decreases and the emission peak shifts to longer wavelength continuously in the Mg2+ doping concentration range of 0.02–0.12. The emission spectra of Y2.96Ce0.04Al(4.8−y)Ga0.20MgyO12 phosphors demonstrate that the codoped Mg2+/Ga3+ ions not only induce the enhancement of Y2.96Ce0.04Al5O12 emission intensity but also lead to the red shift of Y2.96Ce0.04Al5O12 emission peak. The decay lifetimes decrease in Mg2+/Ga3+ codoped Y2.96Ce0.04Al5O12 phosphors due to defects formed by substitutions of Y3+ by Mg2+/Ga3+.

Effect of Si4+ substitution on luminescence of Y3Al5O12:Mn4+

The synthesis, luminescence, and potential applications in white light diodes of Mn4+/Si4+ codoped Y3Al5O12 phosphors are presented. The Mn4+ doped Y3Al5O12 phosphor shows the deep red emission with a strongest emission peak at about 646 nm. By codoping Si4+ in Y3Al5O12:Mn4+, the intensity and peak wavelength of Mn4+ emission are tuned. The appropriately codoped Si4+ can enhance the Mn4+ emission intensity due to the formation of Mn4+-Si4+-O2- pairs. The formed Mn4+-Si4+-O2- pairs interrupts the energy migration from Mn4+ to O2- quenching centers. The codoped Si4+ also induces the blue shift of Mn4+ emission since the substitution of Al23+ by smaller Si4+ leads to a longer Mn-O bond length.