Strontium Aluminate Research Articles

Preparation of Phosphorescent Eu 2+ , Dy 3+ ‐Doped Strontium Aluminate Nanoparticles by Laser Vaporization for the Modification of Therapeutic Contact Lenses

Biologically, effectively regulated light with a wavelength of about 485 nm can support physiological processes in the body and has a positive impact on the human sleep–wake rhythm. However, the application of common light therapy devices is not always practicable and sometimes difficult to integrate into everyday life. Here, miniaturization of therapy devices, for example, in the form of contact lenses, can reduce the handling disadvantages. Especially, contact lenses modified with phosphorescence materials offer this benefit. Herein, a method to prepare phosphorescent Eu2+, Dy3+-doped strontium aluminate nanoparticles (NPs) by laser vaporization of macroscopic Eu2+, Dy3+-doped Sr4Al14O25 particle powder and their integration into polymer-based contact lenses is provided. NPs with a diameter of about 34 nm emit light in the desired therapeutic wavelength region. These novel NPs are biocompatible and do not show any negative effects during the testing of eye irritation safety in a 3D in vitro cornea model.

Luminescence properties of Tb-doped SrAl4O7

In this research terbium-doped strontium aluminate SrAl4O7 samples were synthesized using solid-state synthesis method. X-Ray powder diffraction (XRD) and photoluminescence (PL) measurements were applied for sample characterization. All of them exhibited yellowish-green emission with highest peak at 542 ​nm attributable to 5D4 →7F5 transition. The highest emission intensity was observed in Sr0.98Al4O7:Tb0.02 sample while higher doping levels resulted in decrease of the PL intensities due to concentration quenching. Samples with additional IA group ions for charge compensation were also prepared and their PL properties were measured.

Synchronously activated strontium aluminate nanoflakes anchored functionalized carbon nanofiber nanocomposite for sensitive amperometric detection of food additive: Propyl gallate

The contemporary dietary pattern is ruined by taste enhancers, flavoring agents, and preservatives. Propyl gallate (PG) is an imperative phenolic antioxidant cast-off to inhibit the oxidative mutilation in foodstuffs thereby preventing rancidity. Determination and annihilation of PG are extensively concerned because of its probable lethal effects on human well-being. Herein, we report an electrochemical sensor using SrAl2O4/f-CNF nanocomposite as an efficient electrode modifier with peculiar synergistic quantum confinement effects supporting the formation of heterojunction to facilitate electron transportation between its counterparts. The structural, morphological, and crystalline features of SrAl2O4/f-CNF nanocomposite was thoroughly examined. The proposed sensor possesses a wide linear range (0.1–1104.75 µM) with a remarkably low limit of detection (0.075 µM) and sensitivity (1.142 µA⋅µM−1⋅cm−2) measured at 0.2 V (vs. Ag/AgCl). The reliability of this sensor was evidenced through real-time monitoring of PG in edible oil which is beneficial for food quality monitoring and dropping the danger of abuse of PG in foods.

Investigation of photochromic pigment used for smart textile fabric

The present paper reports a physico-chemical characterization of commercial photoluminescent pigments and details their application on textile fabrics (Cotton and Cotton-PES). An eco-friendly water paste, printing and spin coating techniques were used to apply pigments on textile surface. By using X-ray diffraction diffusion data, Fourier Transform Infrared (FTIR) spectroscopy data, Scanning Electron Microscope (SEM) coupled with Energy- Dispersive X-ray (EDX) analysis, we reveal the presence of some rare earth materials particular Eu and Dy in pigments. These pigments are identified as strontium aluminate rare earth doped materials. Optical properties were conducted using spectrofluorometer for the measurements of emission, excitation and decay times. Green and blue pigments have respectively band emissions around 522 nm and 490 nm under UV excitation. The effect of applying pigments on textile fabric with different concentrations are analyzed. Relying on recorded results, pigments concentration affects the intensity of emissions without wavelength modifications. A notable pigments distribution is obtained on fabric surface using coating technique with interesting results on emission intensity. After fixation, both photoluminescent pigments demonstrate high washing resistance with a smooth surface ‘‘soft hand”. Indeed, the water-based paste is impregnated into the fibers when photoluminescent is applied. It contributed to functional printed and coating fabrics.

Structural Interpretation and Photoluminescence Properties of Sr0:90􀀀xCa0:10Al12O19:Dyx 3+Nanophosphors Synthesis by Combustion system

Objectives: To synthesize a phosphor of more intense, high color purity, and to last longer. Methods: We have synthesized Sr0:90􀀀xCa0:10Al12O19:Dy3+ x (x=0.00, 0.01, 0.03, 0.05, 0.07) phosphors using a low temperature (560  10 )◦C combustion system. X-ray diffraction, Field Emission Scanning Electron Microscopy (FE-SEM), and EDS spectra were used to perform phase identification, morphological examination, and elemental analysis. Spectroscopic photoluminescence techniques of the described phosphor were used to investigate its optical properties. Findings: According to scherrer’s formula, the crystal size of strontium calcium aluminates phosphor is between 12.58 and 84.67 nm. The Dy3+ emission peaks at 475 nm (blue), 573 nm (yellowgreen), and 666 nm (red) in the phosphor. PL emission spectra can be attributed to the 4f-4f transition of Dy3+ ions. The phosphor color purity is 15%, and the average life time is 0.96 ms, indicating that it will survive a long last. The intensity at the wavelengths of 475nm and 575 nm is 40000 counts and 35000 counts, respectively. Novelty: With a 0.10 molar calcium concentration, we have synthesized strontium aluminates phosphor with improved properties. The described phosphor has long-lasting applications as a refractory structural material, great and useful material for pale-orange colorants, and may be employed in many solid-state lighting technologies. Keywords: Strontium Aluminates Phosphor; Paleorange Phosphor; Photoluminescence; Correlated Color Temperature; Combustion System

Vaporization and thermodynamic properties of the SrO-Al2 O3 system studied by Knudsen effusion mass spectrometry.

Strontium aluminates can be used as refractory construction materials at temperatures up to 2000°С or as the materials for immobilization of long-lived radioactive waste. The SrО-Al2 O3 system is one of the more complicated oxide systems used for the creation of new radio-transparent materials. The exploitation of such materials at high temperatures demands the knowledge of the thermal stability of the compounds and solid solutions formed in the SrО-Al2 O3 system. The synthesis of the samples in the SrO-Al2 O3 system was carried out by a ceramic method at 1250°C. The characterization of the samples was accomplished with the use of X-ray diffraction (XRD). The vaporization of the samples under study was performed from a twin tungsten effusion cell using the Knudsen effusion mass spectrometry method. The temperature dependences of partial pressures of vapor species over 4SrO·Al2 O3 , 3SrO·Al2 O3 , SrO·Al2 O3 , SrO·2Al2 O3 and SrO·6Al2 O3 in a wide range of temperatures were determined. The component activities, the Gibbs energies of mixing and the standard enthalpies of individual strontium aluminates were obtained. The thermodynamic properties of the SrO-Al2 O3 system at high temperatures are characterized by negative deviation from ideality. The vaporization processes and thermodynamic properties of the SrO-Al2 O3 system were obtained for the first time.

Preparation and characterization of strontium aluminate/urea-formaldehyde composite: a solution for oxidation-induced darkening problem

PurposeThis study aims to produce homogenously prepared polymer composites by adding two different strontium aluminate derivatives (Sr4Al14O25 and SrAl2O4) to urea-formaldehyde (UF) at different mass concentrations. In the context of this work those strontium-based derivatives were compared in terms of mechanical and luminescent characteristics. Additionally, sodium bicarbonate was integrated with the prepared composites to eliminate/minimize darkening problem, which might arise from the oxidation of Eu +2 to Eu2O3, on the surface of strontium aluminate/urea-formaldehyde composites.Design/methodology/approachIn this study, strontium aluminate/UF composite materials were produced using a compression molding technique. Their mechanical, thermomechanical and luminescence properties were investigated via various characterization methods. Particle size analysis was used to characterize phosphor derivatives, whereas scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) was conducted for morphological examination.FindingsThe darkening problem was prevented by the introduction of sodium bicarbonate into the composite systems. Based on the characterization and test results, the only addition of strontium aluminate reduced the mechanical properties. However, it was seen that the introduction of sodium bicarbonate into the composites improved those properties positively. The appropriate amounts of strontium aluminate and sodium bicarbonate were determined by conducting an experimental optimization study. The optimum composition of the composite materials was obtained by introducing 2% phosphor and 3% NaHCO3.Originality/valueThe approach used in this study has provided a method to solve the darkening problem, which degrades the aesthetic appearance in industrial production.

Preparation of Eu2+, Dy3+, Zr4+ ions co-doped strontium aluminate/molybdate multi-optical functional hybrid pigments for anti-counterfeiting

Eu2+, Dy3+ and Zr4+ ions co-doped strontium aluminate (i.e., SrAl2O4:Eu2+,Dy3+,Zr4+)/molybdate (i.e., Ho2MoO6 or Nd2MoO6) with photo-/mechano-luminescence and allochroic effect as multi-optical functional hybrid pigments were prepared via solid state reactions and subsequent mixing. The phosphor and hybrid pigments were characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, ultraviolet–visible spectroscopy, L∗a∗b∗ color scale analysis, spectrophotometry and mechanoluminescent measurement. The results show that the optimum luminescent emission intensity of SrAl2O4:Eu2+,Dy3+,Zr4+ phosphor can be obtained when 5 mol% Zr4+ ions is doped into the lattice. Under the excitation of 365 nm wavelength, the hybrid pigments prepared with the phosphor and molybdate at a mass ratio of 1:1 present a green broad band emission located at 460–650 nm due to 4f65d1→4f7 transitions of Eu2+ ions. The hybrid pigments have the superior mechanoluminescent property and emit light after being exerted by mechanical stresses. Besides, the hybrid pigments also exhibit an allochroic effect under different illuminants. In addition, the anti-counterfeiting of the hybrid pigments as a promising application was also presented.

Simple Preparation of Photoluminescent and Color-Tunable Polyester Resin Blended with Alkaline-Earth-Activated Aluminate Nanoparticles.

A simple inorganic/organic nanocomposite was used to generate long-lasting phosphorescent pebbles for easy commercial manufacturing of smart products. An organic/inorganic nanocomposite was made from low-molecular-weight unsaturated polyester and rare-earth-activated strontium aluminum oxide nanoparticles doped with europium and dysprosium. The polyester resin was mixed with phosphorescent strontium aluminate oxide nanoparticles and methylethyl ketone peroxide as a cross-linking agent to create a viscous mixture that can be hardened in a few minutes at room temperature. Before adding the hardener catalyst, the phosphorescent strontium aluminate nanoparticles were dispersed throughout the polyester resin in a homogeneous manner to ensure that the pigment did not accumulate. Long-lasting, reversible luminescence was shown by the photoluminescent substrates. The emission was reported at 515 nm upon exciting the pebble at 365 nm. In normal visible light, both blank and luminescent pebbles had a translucent appearance. As a result of UV irradiation, the photoluminescent pebbles produced an intense green color. The three-dimensional CIE Lab (International Commission on Illumination) color coordinates and luminescence spectra were used to investigate the color changing characteristics. Photophysical characteristics, including excitation, emission, and lifetime, were also investigated. Scanning electron microscopy, wavelength-dispersive X-ray fluorescence spectroscopy, and energy-dispersive X-ray analysis were employed to report the surface morphologies and elemental content. Without impairing the pebbles’ original physico-mechanical characteristics, the pebbles showed improved superhydrophobic activity. The current simple colorless long-lasting phosphorescent nanocomposite can be applied to a variety of surfaces, like ceramics, glassware, tiles, and metals.

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.

Long Persistent Luminescent HDPE Composites with Strontium Aluminate and Their Phosphorescence, Thermal, Mechanical, and Rheological Characteristics.

In this work, HDPE/strontium aluminate-based auto glowing composites (SrAl2O4: Eu, Dy (AG1) and Sr4Al14O25: Eu, Dy (AG2)) were prepared, and their phosphorescence studies were conducted. In HDPE/AG1 composites, the green emission was observed at ~500 nm after the UV excitation at 320 nm. The HDPE/AG2 has a blue emission at ~490 nm and, in both cases, the intensity of emission is proportional to the AG1 and AG2 content. The DSC data show that the total crystallinity of both the composites was decreased but with a more decreasing effect with the bulky AG2 filler. The melting and crystallization temperatures were intact, which shows the absence of any chemical modification during high shear and temperature processing. This observation is further supported by the ATR-FTIR studies where no new peaks appeared or disappeared from the HDPE peaks. The tensile strength and modulus of HDPE, HDPE/AG1, and HDPE/AG2 composites were improved with the AG1 and AG2 fillers. The rheological studies show the improvement in the complex viscosity and accordingly the storage modulus of the studied phosphorescent HDPE composites. The SEM images indicate better filler dispersion and filler–matrix adhesion, which improves the mechanical characteristics of the studied HDPE composites. The ageing studies in the glowing composites show that there is a decrease in the intensity of phosphorescence emission on exposure to drastic atmospheric conditions for a longer period and the composites become more brittle.

Synthesis of green phosphor SrAl2O4: Eu2+, Dy3+: Rietveld refinement and optical properties

Strontium aluminate (SrAl2O4), SrAl2O4: Eu2+ and SrAl2O4: Eu2+/Dy3+ phosphors were prepared by solution combustion method. The XRD patterns of the sample were analysed using Rietveld refinement. The analysis confirmed the multiphase structure consisting of hexagonal (P63 space group) and monoclinic (P121 space group) phases. The refinement χ2 values in the range of 2.1–2.8. The crystal structure model was generated based on the refined data. The refined unit cell volume show increment after Eu and Dy doping. The estimated crystallite size is approximately 19 nm and slightly increase after calcination. The emission spectra of the Eu2+ doped SrAl2O4 sample shows a broad emission band with a peak around 500 nm, corresponding to 4f6 5d1 –4f7 transition. With additional Dy3+ doping, the emission peak shifted towards 522 nm, which emitted green light as illustrated by the CIE diagram. The synthesized compounds were also characterized by FTIR and UV-vis for their chemical bonding and energy band gap respectively.

Erosion behavior of Al2O3 + Sm2SrAl2O7 composite thermal barrier coatings

Thermal barrier coatings (TBC) are applied in gas turbines to protect the components from critical operating conditions at high temperatures. Foreign object damage is a major failure cause of turbine components due to erosion of the topcoat ceramic layer of the TBC system. In the present study, Samarium Strontium Aluminate (Sm2SrAl2O7) powders have been synthesized in the laboratory through molten salt synthesis, and thermal barrier coatings were developed using Atmospheric Plasma Spray (APS) technique on an Inconel substrate with NiCrAlY as a bond coat. The erosion behavior of the composite TBC system at temperatures of 200 °C and 800 °C at 30° and 90° impingement angles was analyzed using alumina erodent with a grit size of 50 µm. The erosion weight loss was measured in regular intervals and plotted against erodent mass. The samples exhibited a higher volumetric erosion at 90° and 800 °C. The morphological analysis of developed 70% Al2O3 + 30% Sm2SrAl2O7 composite coatings and eroded areas were performed using XRD, SEM, and surface profilometer. Erosion scars and surrounding deformed areas have been identified in the samples. The microstructure of the eroded areas in the samples showed micro-cutting and plowing as the major material removal mechanisms. Detailed phase analysis of the eroded locations in samples has been reported.

A Simple Fiber Optic Temperature Sensor for Fire Detection in Hazardous Environment Based on Differential Time Rise/Decay Phosphorescence Response

In the present paper we report the development of a simple temperature sensor based on the difference in the temperature dependences of the rise and decay time and of the intensity responses of Eu²⁺, Dy³⁺ doped strontium aluminates. A 374 nm pulsed LED was used as UV source in combination with a lead-in and a lead-out optical fiber to excite the sample and to capture the phosphorescence. We show that because of the power law rise and decay time responses the differential signals measured at earlier instants exhibit the highest sensitivities to temperature over the range from about 5°C to 95°C. Normalized differential signals are characterized by a wide range of linear responses to temperature changes, a sensitivity of up to ≈-1.89 %/°C and a relative error of less than 0.5%. Application to fire prevention is discussed and argumented.

Influence of Eu Ions on White Light Emission of Strontium Aluminate

Influence of Eu Ions on White Light Emission of Strontium Aluminate

Structural, morphological, and photoluminescence properties of red emitting nanophosphors Sr0.85-xCa0.15Al12O19:Dy2+x

Dy2+x (x = 0.000, 0.015, 0.035, and 0.055 % molar concentration) doped strontium calcium aluminates based nanophosphor Sr0.85-xCa0.15Al12O19 was synthesized by combustion technique, utilizing urea as a fuel at an initial temperature of 550 °C. Phase recognition, morphological analysis, and elemental evaluation were accomplished using X-ray diffraction, Field emission scanning electron microscopy (FE-SEM), and EDS spectra. Spectroscopic photoluminescence techniques of the described phosphor maintained optical characteristics. The PL emission spectra revealed the characteristic Dy2+ emission peaks around 666 nm, which can be attributed to the 4F9/2 - 6H11/2 of ions transition. According to the CIE diagram, the optimal emission intensity for SrCaAl12O19:Dy2+0.055 were recorded in the red region. The phosphor described has practical uses as a refractory structural material, and it can be employed in a variety of technologies. We developed strontium aluminates phosphor with better characteristics using a 0.15 M calcium concentration.

Borate polyanions tuning persistent luminescence in Eu and Dy co-doped strontium aluminate

The longest persistent luminescence was obtained in Pechini processed Sr4Al14O25:Eu,Dy with 30–40 mol% B2O3. The amount and presence of borate polyanions induce dopant clustering that yields enhanced persistent luminescence.

Investigations of Thermal Stability and Spectroscopic Features of Sm3+ Doped Strontium Aluminate Glasses

In the present work, a series of Sm3+ doped transparent strontium aluminate glasses with the composition Al2O3-(3-x)SrO: xSm3+ (x = 0, 0.01, 0.03, 0.06, 0.1, 0.2) were fabricated by a containerless process using an aerodynamic levitation furnace. The structural characteristics, density, Vicker’s hardness, and thermal and spectroscopic behaviors of these glasses were investigated. All the glasses exhibit excellent thermal stabilities (Tg ≥ 792 °C) and the glass-forming ability is enhanced with the increasing content of Sm3+. The emission spectra recorded under an excitation of 404 nm show four emission transitions as a result of 4G5/2 translated to the lower states of 6H5/2, 6H7/2, 6H9/2, and 6H11/2, and a bright orange-reddish luminescence can be observed in Al2O3-(3-x)SrO: xSm3+ glasses. The high thermal stability, good glass-forming ability and excellent hardness provide new options for the development of visible orange-reddish lasers and smart photoluminescent glass coating materials.

Effects of temperature on the time responses of strontium aluminates

In this paper we study the effect of temperature on the rise and decay time responses of Eu and Eu, Dy doped strontium aluminates. Normalized switch on and switch off time responses are used to estimate the share of phosphorescence in the observed luminescence. The parameters of the power law time responses related to the relative share of phosphorescence in luminescence and to the rise/decay rates are found to be strongly temperature dependent. The results show that unlike luminescence intensity, the overall efficiency of phosphorescence increases strongly with temperature and reaches a maximum around 65 °C. Thе maximum correlates with the activation energy of the samples and depends on their doping and fabrication technology.

Thermodynamic analysis of strontium deoxidizing ability in liquid iron at presence of aluminum

Phase diagram of the ternary oxide system FeO - SrO -Al2O3 was constructed for the first time. In this system, the following compounds can be formed: hercynite FeAl2O4 and five strontium aluminates - Sr4Al2O7 , Sr3Al2O6 , SrAl2O4 , SrAl4O7 , SrAl12O19 . According to the calculations performed, solid solutions of oxides are not formed in the system, as it is confirmed by the literature data. In the course of modeling, the optimal energy parameters of the theory of subregular ionic solutions were selected for the components of the oxide melt (FeO, SrO, Al2O3 ). Thermodynamic analysis of strontium deoxidizing ability in liquid iron at presence of aluminum was carried out using the technique for constructing the surface of solubility of strontium and aluminum in metal for steelmaking temperatures (1550 and 1600 °C) and carbon concentrations of 0.1 and 0.4 %. The equilibrium constants of the reactions of formation of strontium aluminates Sr3Al2O6 and SrAl2O4 from the components of the metal melt were calculated for the temperature range of 1550 - 1650 °C. It was found that the rest of strontium aluminates can be formed in liquid metal only at temperatures above 1750 °C. The base of thermodynamic data for the studied systems is given: temperature dependences of equilibrium constants for reactions occurring between components; values of interaction parameters of the first order (according to Wagner) for elements in liquid iron; values of energy parameters of the theory of subregular ionic solutions (for oxide melt). It follows from the calculations that the formation of strontium monoaluminate SrAl2O4 and corundum Al2O3 is most probable as the interaction products in Fe -Al - Sr - O and Fe -Al - Sr - C - O systems.