Rare Earth Aluminum Research Articles

Insight into leaching of rare earth and aluminum from ion adsorption type rare earth ore: Adsorption and desorption

Clay minerals are inferred to be the primary host materials for ion-exchangeable rare earth in ion adsorption type rare earth ore (IAREO). During the rare earth leaching process, the adsorption and desorption reactions of the cations controlling the leaching process continue to occur at the clay minerals-leaching agent solution interface. In order to understand the leaching mechanism and behavior of rare earth and co-leached aluminum, adsorption, competitive adsorption, and desorption experiments were carried out using kaolin as a typical clay mineral. The powerful electrostatic attraction and concentration driving forces facilitate the adsorption of cations. The adsorption ability and competitive adsorption ability of cations depend on their charge, hydration radius, and hydrolysis properties, and decrease in the order of La3+, Y3+, Al3+, Mg2+, and NH4+. The desorption of rare earth and aluminum is positively affected by the concentration-driving force exerted by high concentrations of Mg2+ and NH4+, with the order of the desorption ability being opposite to the adsorption ability. However, unspecified interactions between clay mineral particles enhanced by high-concentration desorbents, especially by Mg2+ than NH4+, will adversely affect desorption reactions, which result in lower desorption efficiencies of rare earth and aluminum obtained with magnesium sulfate compared to those obtained with ammonium sulfate at high concentrations. Solid-phase Al(OH)3 generated at a high peak aluminum concentration leads to a considerably delayed aluminum efflux, thereby partially separating the rare earth from aluminum during the actual column leaching process. To advance the mining technology of IAREO by selectively improving the rare earth leaching efficiency with minimal leaching agent consumption, higher charged cations with concentrations limited to suitable levels should be preferred as leaching agents.

Microstructure design to achieve optimal strength, thermal stability, and electrical conductivity of Al-7.5wt.%Y alloy

Aluminum-rare earth (Al-RE) alloys are being increasingly evaluated as new generation heat resistant conductor materials owing to their superior thermal stability, which is attributed primarily to the limited solubility of RE elements in the Al matrix and resulting RE-containing eutectic intermetallic compounds formed in their microstructure. This paper describes the main results from an experimental investigation into tailoring the contrasting strength-electrical conductivity characteristics of an Al–Y eutectic alloy by manipulating several microstructural features using multi-passes cold drawing and annealing processes. High strength of the alloy was achieved not only owing to substantial grain refinement, high dislocation density, and β-Al3Y intermetallic phases but also by forming stacking faults and inducing <111> fiber texture via cold drawing. The alloy was found to preserve fine grains in its annealed state, which is attributed to the β-Al3Y intermetallic phases at grain boundaries stimulating nucleation but also preventing grain growth. Moreover, <111> fiber texture and some stacking faults remained stable during annealing, while the β-Al3Y intermetallic phases spheroidized. As a result, the alloy exhibited extraordinary thermal stability with some loss of strength originating mainly from the reduction in dislocation density upon annealing. Importantly, the novel Al–Y wires exhibit superior heat resistance over the commercial Al–Zr wires. Finally, electrical conductivity of the Al–Y wires improved with annealing, which is primarily due to the release of interfacial energy accompanying spheroidization of β-Al3Y phases and underlying decrease in interfacial scattering at β-Al3Y/α-Al interfaces.

Probing the effect of R-cation radii on structural, vibrational, optical, and dielectric properties of rare earth (R=La, Pr, Nd) aluminates

The present study correlates the effect of R-cation radii on structural, vibrational, optical, and dielectric properties of rhombohedral rare earth aluminates RAlO3 (R = La, Pr, Nd). The polycrystalline samples of RAlO3 have been synthesized using sol-gel synthesis technique. Pure rhombohedral phase of RAlO3 samples has been confirmed with X-ray diffraction. Systematic decrements in the lattice parameter, bond length, and bond angle have been observed, giving rise to structural distortion due to decrease in ionic radii of R-cation. The phononic properties of RAlO3 have been investigated through Raman spectroscopy, where the degree of distortion of AlO6 octahedra can be analyzed with the peak position of Eg and A1g modes. An increase in the energy bandgap with decreasing R-cation radii shows an interconnection with the decrease in Al–O bond length. Interestingly, the decreasing dielectric constant with decreasing ionic radii of R-cation has been correlated with the difference in electronegativity of cation(R3+)-anion(O2−) pair. Also, a positive linear relationship between dielectric constant and energy bandgap has been investigated using Penn model.

Preparation of epoxy resin/rare earth doped aluminate nanocomposite toward photoluminescent and superhydrophobic transparent woods

A translucent wooden substrate with long-lasting phosphorescence, high photostability and durability, tough surface, ultraviolet protection, high optical transmittance, and superhydrophobicity was developed. This long-lasting phosphorescent wooden substrate is able to continue emitting light for extended time periods. Lignin-modified wood (LMW) was immobilized with a solution of epoxy resin (ER) and rare-earth doped aluminate (REDA) phosphor nanoparticles (NPs). For an improved dispersion of pigment, REDA was synthesized in a nanoscale particle size, and characterized by transmission electron microscopy (TEM) to indicate a particle size of 8–14 nm. The crystal structure of REDA nanoparticles was also proved by X-ray diffraction (XRD). For an improved production of long-persistent phosphorescent colorless woods, REDA must be well-dispersed in MAA without aggregation. Absorption and emission, as well as decay and lifetime spectra were explored. The morphologies of the wooden substrates with different ratios of REDA were investigated by scanning electron microscopy (SEM), X-ray fluorescence (XRF) analysis, Fourier transform infrared spectra (FT-IR), elemental mapping, and energy-dispersion X-ray (EDXA). The phosphorescent woods show changes in color from colorless to green under ultraviolet (UV) irradiation, and to yellowish-green in the dark, as proved by the colorimetric parameters of the CIE Lab system. The afterglow wood samples display an absorbance band at 365 nm and two phosphorescent bands at 431 and 520 nm. Improved UV shielding, photostability, and hydrophobicity were explored. With increasing REDA ratio, both static contact and slide angles are found to improve in the ranges of 147.6°–163.6° and 9°–14°, respectively. The long-lasting photoluminescence is optimized at a REDA ratio of 8%. The present strategy shows a large-scale production approach of multiple functional woods for many potential applications, such as smart glow in the dark windows and safety signs.

Preparation, Microstructure and Thermal Conductivity of Plasma-Sprayed (Y0.8Gd0.2)3Al5O12 Coatings

Garnet-type rare earth aluminate compounds are one class of promising potential candidate materials for thermal barrier coatings (TBCs). In this paper, (Y0.8Gd0.2)3Al5O12 (GYAG) coatings are fabricated by air plasma spraying, with the microstructure, high-temperature phase stability, and thermal conductivity investigated. The results showed that the as-deposited GYAG coating was relatively dense, and contained garnet-type (Y0.8Gd0.2)3Al5O12 phase and a small amount of (Y,Gd)AlO3 and amorphous phases. The crystallized GYAG coating exhibited good phase stability from room temperature to 1450 °C. The coating had the lowest thermal conductivity of 1.17 W·m−1·K−1 at 800 °C, approximately 15% lower than that of the yttria-stabilized zirconia (YSZ) coating. After heat treatment at 1100 °C, the coating became denser with some fine grain precipitation, and formed a number of transverse and longitudinal cracks.

Longitudinal piezoelectric, elastic, and dielectric properties of rare-earth aluminum nitride alloys determined by density-functional perturbation theory

The superior piezoelectric (PE) performance of devices based on thin-films of wurtzite (w) w-${\mathrm{Sc}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}\mathrm{N}$ alloys has motivated research efforts to determine the material properties of other alloys of aluminum nitride and rare-earth nitride (w-${\mathrm{RE}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}\mathrm{N}$). The longitudinal PE, elastic and dielectric properties of substitutional w-${\mathrm{RE}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}\mathrm{N}$ alloys have been calculated with density-functional perturbation theory. The rare-earth elements in the simulations stand for scandium, yttrium and seven lanthanides: lanthanum, neodymium, gadolinium, dysprosium, erbium, ytterbium, and lutetium. The structure of the investigated alloys is modeled with special quasirandom $2\ifmmode\times\else\texttimes\fi{}2\ifmmode\times\else\texttimes\fi{}2$ supercells at rare-earth nitride fractions $x$ of 0.0625 and 0.25. The $4f$ electrons of the lanthanides are incorporated in the pseudopotential core, an approach supported by the standard model of lanthanide chemistry. An increase of the PE stress coefficient ${e}_{33}$ and a softening of the stiffness coefficient ${c}_{33}^{E}$ are found for all investigated alloys for $x$ = 0.25, when compared to w-AlN. This leads to significant improvements of the PE strain effective coefficient ${d}_{33,f}$ of films of these alloys. For w-${\mathrm{Lu}}_{0.25}{\mathrm{Al}}_{0.75}\mathrm{N}$, the ${d}_{33,f}$ increases by $\ensuremath{\sim}100%$ compared to pure w-AlN. Increased displacement-response internal-strains and Born effective charges are demonstrated for all alloys at $x$ = 0.25, in a manner consistent with the behavior of w-${\mathrm{Sc}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}\mathrm{N}$ alloys, suggesting shared intrinsic properties for the entire w-${\mathrm{RE}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}\mathrm{N}$ alloy family. Distortions of the alloy structure, correlated with the ionic radius of the rare earths, negatively affect their PE properties. At a small fraction $x$ = 0.0625, the alloys incorporating Sc, Y, Er, Yb, and Lu possess PE coupling coefficients ${k}_{33,f}^{2}$ greater than for w-AlN.

Tm,Ho:Ca(Gd,Lu)AlO4 crystals: Crystal growth, structure refinement and Judd-Ofelt analysis

“Mixed” calcium rare-earth aluminate laser host crystals Ca(Gd,Lu)AlO4 (CALGLO) with up to 10.8 at.% Lu codoped with Tm3+ and Ho3+ ions are grown by the Czochralski method along the [001] direction. The segregation of rare-earth ions is studied. The crystal structure is refined by the Rietveld method. Tm,Ho:Ca(Gd,Lu)AlO4 crystallizes in the tetragonal system (sp. gr. I4/mmm) exhibiting a K2NiF4 type structure. The lattice constants are a = 3.6585(6) Å and c = 11.9660(9) Å for a crystal with a composition of CaGd0.8947Lu0.0551Tm0.0448Ho0.0054AlO4. The stability of Ca(Gd,Lu)AlO4 solid-solutions is discussed. The polarized Raman spectra are measured, revealing a most intense mode at 311 cm−1 and a maximum phonon frequency of ∼650 cm−1. The polarized absorption spectra are measured. The transition intensities for the Ho3+ ion are analyzed using the modified Judd-Ofelt theory accounting for configuration interaction.

Development of silica-coated rare-earth doped strontium aluminate toward superhydrophobic, anti-corrosive and long-persistent photoluminescent epoxy coating.

Long-persistent phosphorescent smart paints have the ability to continue glowing in the dark for a prolonged time period to function as energy-saving products. Herein, new epoxy/silica nanocomposite paints were prepared with different concentrations of lanthanide-doped aluminate nanoparticles (LAN; SrAl2 O4 :Eu2+ ,Dy3+ ). The LAN pigment was firstly coated with silicon dioxide (SiO2 ) utilizing the heterogeneous precipitation technique to provide LAN-encapsulated between SiO2 nanoparticles (LAN@SiO2 ). The epoxy/silica/lanthanide-doped aluminate nanoparticles (ESLAN) nanocomposite paints were coated on steel. The prepared ESLAN paints were studied by transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray fluorescence (XRF) analysis, and energy-dispersive X-ray spectroscopy (EDS). The transparency and coloration properties of the nanocomposite coated films were explored by CIE Lab parameters and photoluminescence spectra. The ultraviolet-induced luminescence properties of the transparent coated films demonstrated greenish phosphorescence at 518 nm upon excitation at 368 nm. Both hardness and hydrophobic activities were investigated. The anticorrosion activity of the nanocomposite films coated onto mild steel substrates immersed in aqueous sodium chloride (NaCl(aq) ) (3.5%) was studied by electrochemical impedance spectroscopy (EIS). The silica-containing coatings were monitored to exhibit anticorrosion properties. Additionally, the nanocomposite films with LAN@SiO2 (25%) exhibited the optimized long-lasting luminescence properties in the dark for 90 min. The nanocomposite films showed highly reversible and durable long-lived phosphorescence.

Design of thermal and environmental barrier coatings for Nb-based alloys for high-temperature operation

The design of thermal and environmental barrier coatings (T/EBCs) applied to Nb-based alloys for high-temperature operation (>1200 °C) was studied. Different multilayer T/EBCs consisting of rare earth aluminates, silicates, and zirconates (with Y 3 Al 5 O 12 (YAG), Y 2 SiO 5 (YMS), and Gd 2 Zr 2 O 7 (GZO) as exemplars) are proposed. Mechanics models were used to determine the magnitude of thermal stresses developed and the tendency for delamination or penetration cracking. The calculated energy release rates (ERRs) for crack formation show that the T/EBC composed of a porous YAG layer (porosity > 0.15) and a dense YAG + YMS layer is effective in preventing the delamination and can potentially arrest cracks penetrating from the surface before reaching the substrate. Phase equilibria calculations indicate that all combinations are stable to above their expected use temperatures. The greatest likelihood for melting is the scenario where a YAG + YMS solid mixture contains excess SiO 2 due to process variability, but even in this case the melting temperature, 1430 °C, exceeds the corresponding temperature in the prescribed temperature profile. • Multilayer thermal/environmental barrier coatings inhibit crack growth. • Rare earth aluminate and silicate coatings are suitable for Nb-based alloy. • Phase mixtures have better properties but lower melting temperatures. • Columnar porosity in coating reduces energy release rate for crack formation.

Development of epoxy/rice straw-based cellulose nanowhiskers composite smart coating immobilized with rare-earth doped aluminate: Photoluminescence and anticorrosion properties for sustainability

Novel epoxy resin (E)/CNW nanocomposite coatings were developed with different total contents of rare-earth doped aluminate nanoparticles (REA NPs). The produced epoxy-cellulose nanowhiskers-rare earth doped aluminate nanoparticles (E-CNW-REA) coatings were applied onto mild steel. The epoxy/CNW nanocomposite coatings were characterized by X-ray fluorescence analysis (XRF), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXA), transmission electron microscope (TEM) and infrared spectra (FT-IR). Both colorimetric properties and transparency of the nanocomposite coatings were proved by exploring UV–Vis absorption spectroscopy and CIE Lab parameters. The hardness and superhydrophobic properties were also explored. The photoluminescent transparent coatings showed an excitation at 365 nm, and a bright green emission wavelength at 517 nm under UV light. The corrosion protection performance of the coated mild steel samples soaked in an aqueous solution of sodium chloride (3.5%) was investigated using electrochemical impedance spectroscopy (EIS). The coatings with CNW were found to have anti-corrosion properties. Moreover, the nanocomposite coating with CNW (1 w%) was monitored to exhibit the most pronounced long-persistent photoluminescence for 60 min in the dark. The photoluminescent coatings exhibited highly durable long-lasting phosphorescence. Thus, the current strategy can be considered as a simple promising technology for industrial production of anti-corrosive, superhydrophobic and long-persistent phosphorescent.

Mechanical and Thermophysical Properties of Rare-Earth Aluminate Glasses and Melts

Mechanical and Thermophysical Properties of Rare-Earth Aluminate Glasses and Melts

Терагерцовая спектроскопия магнитоэлектрика HoAl-=SUB=-3-=/SUB=-(BO-=SUB=-3-=/SUB=-)-=SUB=-4-=/SUB=-

Experimental and theoretical study of submillimeter (terahertz) spectroscopic and magnetic properties of the rare-earth aluminum borate HoAl3(BO3)4 were performed at temperatures 3–300 K. In the transmittance spectra a number of resonance lines were detected at frequencies 2–35 cm–1 for different radiation polarizations. These modes were identified as transitions between the lower levels of the ground multiplet of the Ho3+ ion split by the crystal field, including both transitions from the ground state to the excited ones and transitions between the excited states. The established excitation conditions of the observed modes and the simulation of the spectra made it possible to separate the magnetic and electric dipole transitions and to determine the energies of the corresponding states, their symmetry, and the matrix elements of the transitions. Low-frequency lines that do not fit into the established picture of the electron states of Ho3+ were also found; these lines, apparently, correspond to the ions with the distorted by defects local symmetry of the crystal field.

33-21

Experimental and theoretical study of submillimeter (terahertz) spectroscopic and magnetic properties of the rare-earth aluminum borate HoAl3(BO3)4 were performed at temperatures 3–300 K. In the transmittance spectra a number of resonance lines were detected at frequencies 2–35 cm–1 for different radiation polarizations. These modes were identified as transitions between the lower levels of the ground multiplet of the Ho3+ ion split by the crystal field, including both transitions from the ground state to the excited ones and transitions between the excited states. The established excitation conditions of the observed modes and the simulation of the spectra made it possible to separate the magnetic and electric dipole transitions and to determine the energies of the corresponding states, their symmetry, and the matrix elements of the transitions. Low-frequency lines that do not fit into the established picture of the electron states of Ho3+ were also found; these lines, apparently, correspond to the ions with the distorted by defects local symmetry of the crystal field.

Visible and near-infrared emitting heterotrimetallic lanthanide-aluminum-sodium 12-metallacrown-4 compounds: discrete monomers and dimers.

The luminescence properties of two types of heterotrimetallic aluminum-lanthanide-sodium 12-metallacrown-4 compounds are presented here, LnNa(ben)4[12-MCAl(III)N(shi)-4] (LnAl4Na) and {LnNa[12-MCAl(III)N(shi)-4]}2(iph)4 (Ln2Al8Na2), where Ln = GdIII, TbIII, ErIII, and YbIII, MC is metallacrown, ben- is benzoate, shi3- is salicylhydroximate, and iph2- is isophthalate. The aluminum-lanthanide-sodium metallacrowns formed with benzoate are discrete monomers while, upon replacement of the benzoate with the dicarboxylate isophthalate, two individual metallacrowns can be joined to form a dimer. In the solid state, the terbium version of each structure type displays emission in the visible region, and the erbium and ytterbium complexes emit in the near-infrared. The luminescence lifetimes (τobs) and quantum yields have been collected under ligand excitation (QLLn) for both LnAl4Na monomers and Ln2Al8Na2 dimers. Several of these values tend to be shorter (luminescence lifetimes) and smaller (quantum yields) than the corresponding values recorded for the structurally similar gallium-lanthanide monomer and dimer 12-MC-4 molecules. However, the quantum yield value recorded for the visible emitting Tb2Al8Na2 dimer, 43.9%, is the highest value observed in the solid state to date for a TbIII based metallacrown.

Determination of zirconium and hafnium in Egyptian monazite by ICP-OES

The determination of Zirconium and Hafnium in presence of each other in geological sample by using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) technique had established, the physical parameters of the instrument were adjusted and the suitable zirconium and hafnium lines were selected to give the most accurate determination, the sensitivity of each line was tested by a solution of 20 ppm zirconium mixed with 1 ppm hafnium to obtain the most sensitive lines which were 339.198 nm for zirconium and 239.336 nm for hafnium. The interference effect was studied which prove the interference effect of the major elements of monazite as Uranium, Thorium, Rare earth elements, Iron and Aluminium on the determination of the elements under studying. The sample used in this work was a mineral of monazite from black beach sand which was upgraded of about 97% purity; the sample was leached by concentrated sulfuric acid (H2SO4) at 250 0C to separate zircon which contains zirconium and hafnium as a residue which dried, weighed and fused by sodium hydroxide for complete decomposition and measured by ICP-OES (Nuclear Materials Authority, Egypt) on the selected lines.

Development of Mechanically Reliable and Transparent Photochromic Film Using Solution Blowing Spinning Technology for Anti-Counterfeiting Applications.

Photochromic materials have attracted broad interest to enhance the anti-counterfeiting of commercial products. In order to develop anti-counterfeiting mechanically reliable composite materials, it is urgent to improve the engineering process of both the material and matrix. Herein, we report on the development of anti-counterfeiting mechanically reliable nanocomposites composed of rare-earth doped aluminate strontium oxide phosphor (RESA) nanoparticles (NPs) immobilized into the thermoplastic polyurethane-based nanofibrous film successfully fabricated via the simple solution blowing spinning technology. The generated photochromic film exhibits an ultraviolet-stimulated anti-counterfeiting property. Different films of different emissive properties were generated using different total contents of RESA. Transmission electron microscopy was utilized to investigate the morphological properties of RESA NPs to display a particle diameter of 3–17 nm. The morphologies, compositions, optical transmittance, and mechanical performance of the produced photochromic nanofibrous films were investigated. Several analytical methods were employed, including energy-dispersive X-ray spectroscopy, scanning electron microscopy, and Fourier-transform infrared spectrometry. The fibrous diameter of RESA-TPU was in the range of 200–250 nm. In order to ensure the development of transparent RESA-TPU film, RESA must be prepared in the nanosized form to allow better dispersion without agglomeration in the TPU matrix. The luminescent RESA-TPU film displayed an absorbance intensity at 367 nm and two emission intensities at 431 and 517 nm. The generated RESA-TPU films showed an enhanced hydrophobicity without negatively influencing their original appearance and mechanical properties. Upon irradiation with ultraviolet light, the transparent nanofibrous films displayed rapid and reversible photochromism to greenish-yellow without fatigue. The produced anti-counterfeiting films demonstrated stretchable, flexible, and translucent properties. As a simple sort of anti-counterfeiting substrates, the current novel photochromic film provides excellent anti-counterfeiting strength at low-cost as an efficient method to develop versatile materials with high mechanical strength to create an excellent market as well as adding economic and social values.

Compositional screening of Ce-doped (Gd,Lu,Y)3(Al,Ga)5O12 ceramics prepared by quenching from melt and their luminescence properties

Quenching from the melt using an Optical Floating Zone furnace was investigated as a possible high-throughput preparation method in order to screen novel scintillating materials. To validate this method, polycrystalline rare-earth aluminum garnets and yttrium gallium aluminum garnets were synthesized and characterized by X-ray diffraction, photoluminescence and radioluminescence emission spectra as well as radioluminescence imaging and compared to the previously reported properties of those materials. In order to achieve rapid, but quantitative comparison of the materials, pellets fabricated from the synthesized powders were sintered; two different sintering conditions were investigated and compared. A simplistic energy deposition and light absorption model for brightness of opaque samples under X-ray irradiation was developed to estimate the relative scintillation efficiency of the materials. Based on the results, Y3Al5O12, LuY2Al5O12 and GdY2Al5O12 seem to have the highest scintillation efficiency among the prepared samples.

Simultaneous hyperaccumulation of rare earth elements, manganese and aluminum in Phytolacca americana in response to soil properties

The plant Phytolacca americana L. simultaneously hyperaccumulates manganese (Mn) and rare earth elements (REEs), but the underlying mechanisms are largely unknown. In this study, P. americana and the corresponding rhizosphere soil samples were collected from an ion-adsorption REE mine area in China, and the elemental composition and soil properties were analyzed in order to explore the relationship between metal accumulation and soil properties. The results show that P. americana accumulates high concentrations of REEs (up to 1040 mg kg−1), Mn (up to 10400 mg kg−1) and aluminum (Al) (up to 5960 mg kg−1) in leaves. The REE concentrations in leaves were positively correlated with those of Al, Fe and Zn, while light REE concentrations were negatively correlated with P concentrations (p < 0.05). The soil properties explained 81.7%, 72.9% and 67.1% of REEs, Mn and Al accumulated in P. americana, respectively. The variation of REE accumulation in P. americana was primarily explained by plant available P (24.4%), pH (12.9%), TOC (9.4%) and total P (7.7%). The accumulation of Mn was primarily explained by plant available REEs (42.9%) and available Al (13.1%) while Al in P. americana was primarily explained by soil pH (14.4%). This study suggests the potential by regulation of soil properties in improving the efficiency of phytoextraction for REEs by hyperaccumulators.

Epitaxial Growth of Single Crystal YAG for Optical Devices

We report the latest progress on fabrication of rare earth doped single crystal yttrium aluminum garnet (YAG) core/undoped YAG cladded fibers. Rare-earth doped single crystal core fibers were grown with laser heated pedestal growth methods. In a second step, epitaxial methods were used to grow a single crystalline undoped YAG cladding onto the core fiber. Hydrothermal and liquid phase epitaxy methods utilize the core doped fiber as the seed. X-ray diffraction of cladding reveals an equilibrium (110) morphology. Energy-dispersive X-ray spectroscopy analysis shows there is minimal diffusion of rare-earth dopants into the cladding structure. The use of scandium doping is shown to substitute at the Al3+ site, thereby allowing an additional tunability of refractive index of core structure material besides conventional Y3+ site dopants. The use of these epitaxial growth methods enables material compatibility, tuning of refractive index, and conformal growth of cladding structures onto core fibers for optical devices.

Mechanoluminescence behaviour on Eu2+/Dy3+ activated SrAl2O4 phosphor

Synthesis of Eu/Dy rare earth doped strontium aluminate phosphor or material with varying concentration of co-dopant (Dy3+) and fixed concentration of dopant (Eu2+) is reported inside the manuscript. Phosphor are prepared and synthesized by using the technique of solid-state reaction in reducing atmosphere and activated charcoal was used to create the atmosphere. Mechanoluminescence pattern were recorded for variable concentration of doping / co-doping ions and it is found with the increment in the concentration of co-dopant up-to 1 mol%, the ML intensity increases and after that the ML intensity decrement occurs due to the phenomenon of concentration quenching. Similarly, for the optimized concentration the ML pattern obtained for gamma – irradiated phosphor and it shows linear response with dose so our study supports the ML dosimeter application to detect the radiation via mechanoluminescence study. The suitable models are compared herein, which are already reported by so many authors.