Aluminate Phosphors Research Articles

Preparation and long-persistent luminescence study on strontium aluminate particles dip-coated compound textile

In this study, we prepared long-persistent luminescent strontium aluminate/cotton compound fabric using green tea natural dye and evaluated its functional properties. Green tea natural pigments were extracted at different extraction temperature, extraction time, and bath ratio. We determined the optimum parameters of the technique by comparing the absorbance. The dyeing rate and UV protection of the strontium aluminate particles dip-coated compound textile were optimized using the response surface methodology (RSM). The results indicated that the dye-uptake of the sample was significantly different. However, the UV protection property was not significantly different. The dyeing time was the most significant factor influencing dye-uptake. Optimum dyeing effect and UV protection (K/S value = 1.6621 and UPF value = 38.581, respectively) were attained at a dyeing temperature of 89.92 °C, the dyeing time of 67.06 min, and bath ratio of 42.28. The compound fabric dyed using in-bath mordant and dip-coated with strontium aluminate phosphor exhibited long-persistent luminescence property that was effective for 120 min.

Tuning the luminescence properties of Mn4+‐activated CaYAlO4 phosphor by co‐doping cations for indoor plant cultivation

AbstractTo fulfil the demands of high‐power plant growth lamps, cation co‐doping is an effective way to tune the photoluminescence properties of manganese (Ⅳ)‐activated aluminate phosphors. Therefore, we managed to synthesize a series of cations co‐doped CaYAlO4:xMn4+, mSr2+, M+ (M+ = Li+, Na+, and K+) (CYAO:Mn, Sr, M) far‐red‐emitting phosphors. The excitation spectrum of these phosphors contained two excitation bands, and the opposite effects of these two bands on the luminescence intensity have been observed with the increase of Mn4+ concentration. By adding 0.1 mol Sr2+ ions to replace Ca2+ site, the emission intensity and thermal stability of CYAO:Mn phosphors can be enhanced. Furthermore, the luminescence properties of CSYAO:Mn can be further improved by co‐doping monovalent alkali metal ions to serve as charge compensators, the increased number of Mn4+ luminescence centers. Moreover, 0.6 mol% Na+ can increase the initial emission intensity of the phosphors by 117% as the best ratio. The characteristic emission spectrum of the phosphors CYAO:Mn,Sr,M correspond to the phytochrome PFR of plants. These experiments and characterization results have certified that these phosphors have a potential application in indoor plants cultivation.

Dysprosium activated strontium aluminate phosphor: A potential candidate for WLED applications

A series of dysprosium activated strontium aluminate phosphors (SrAl2O4:xDy3+: x = 0.1, 0.2, 0.3, 0.4 and 0.5%) are prepared by conventional solid state reaction method. The structure of the prepared phosphors is analyzed by XRD. Results confirm that the crystal structure of the synthesized phosphors is monoclinic with space group P21. Morphology and microstructure of the synthesized phosphors is analyzed using FESEM and TEM analysis respectively. Optical properties are analyzed by using Raman and PL spectra. The characteristic peak observed at 465 cm−1 corresponds to bending mode of O–Al–O bonds in corners sharing with [AlO4]5- tetrahedral. The strongest PL emission band observed at 470 nm can be assigned to 4F9/2 - 6H15/2 transition in blue region when subjected to the ultraviolet excitation of wavelength 347 nm. White light is emitted by combination of red, yellow and blue emissions and is confirmed by CIE chromatic coordinate graph and the probable mechanism responsible for emission of the white light is explained in detail.

Structural and photoluminescent investigations of SrAl2O4:Eu[formula omitted],RE[formula omitted] improved nanophosphors for solar cells

The long afterglow green emitting materials were prepared by fast gel-combustion procedure (600 °C) using urea as fuel. This paper reports the improvement in photoluminescence intensity and persistency of Eu2+ incorporated long-persistent SrAl2O4 nanophosphors by the addition of rare earth ions (Dy3+, Pr3+, Y3+) as codopants. The materials were investigated using X-ray diffraction (XRD), Fourier transformation infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. X-ray diffraction analysis exhibited the formation of pure SrAl2O4 phase with monoclinic crystal system and space group P21. FTIR spectra were used to determine the stretching and bending modes of vibrations to confirm the formation of metal–oxygen bonds. The microstructures were observed using SEM and TEM analysis. For the synthesized strontium aluminate phosphors, the photoluminescence characteristics including excitation, emission and decay kinetics were also examined. PL emission spectra, recorded at the excitation wavelength of 362 nm, exhibited the characteristics peak at 510 nm corresponding to the parity allowed 5d–4f electronic transition of Eu2+ ions. The phosphorescence intensity of the materials were greatly enhanced on addition of codopants (Dy3+, Pr3+, Y3+), without any change in the position of the peak in spectra. The outcomes of these investigations made the focused materials worthy for the applications in the solar cells and lighting technology.

Effect of Sr on the luminescence properties of Eu3+ activated xZnO-(1-x) SrO-Al2O3 phosphors

Europium-doped xZnO-SrO-Al2O3 (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) phosphors were synthesized by the traditional Solid-State Reaction (SSR) method. The structure of the phosphors prepared was analysed with the x-ray diffraction technique. The xZnO-(1-x) SrO-Al2O3:Eu3+ (0.1 mol%) (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) exhibits varying PL intensity and is maximum for 0.8ZnO-0.2SrO-Al2O3: Eu3+ (0.4 mol%) and hence treated as the most prominent phosphor among these combinations. In the photoluminescence spectrum of the phosphors prepared, a sequence of emission bands were visible at various wavelengths viz., 576, 586, 602, 620, 656 and 702 nm as a result of the transitions of Eu3+ ions [5D0 - 7Fj where (j = 0–4)] and an excitation spectrum at 620 nm. An efficient orange-red phosphor thus developed capable of yielding a quantum efficiency of about 12%. Studies revealed that the commercially available red phosphors having an efficiency of only 9.6% (λex = 394 nm) & 4.2% (λex = 395 nm). Hence the current sample could be an ideal alternative for an efficient phosphor near UV LEDs. The mechanoluminescence of the 0.8ZnO-0.2SrO-Al2O3: Eu3+ (0.4 mol%) phosphor was also measured. The phosphor composition was analysed using XPS. The present paper also reports the thermoluminescence and OSL properties of Europium doped Zinc Strontium Aluminate phosphor at different gamma-ray dosages. Peak shape method was employed to evaluate kinetic parameters like activation energy, frequency factor and symmetry factor.

Discovery of blue-emitting Eu2+-activated sodium aluminate phosphor with high thermal stability via phase segregation

Thermally stable phosphors are crucial for the application in phosphor-converted white light-emitting diodes. This paper reports the evolution of phase compositions in nominal Na2−xAl2B2O7:xEu (x = 0.02–2.0) upon replacing Na atoms by Eu atoms. Eu2+-activated blue-emitting phosphor was discovered through phase segregation combined with related analyses. The structure, phase composition and related luminescent properties were investigated by X-ray powder diffraction, backscattered electron image combined with elemental mapping, cathodoluminescence-combined scanning electron microscope, and temperature-dependent emission spectra, etc. Analyses results suggest that EuBO3 phase segregates upon the gradual replacement of Na by Eu atoms, which is accompanied by phase transformation from Na2Al2B2O7:Eu2+ to NaAl11O17:Eu2+ and dramatic enhancement of blue emission. The broad emission band is peaking at around 470 nm under UV irradiation. The internal quantum efficiencies of nominal Na0.4Al2B2O7:1.6Eu and Na0.2Al2B2O7:1.8Eu are 58.6% and 60.2%, respectively, which contain both NaAl11O17 and EuBO3 phase. The emission intensity for these two samples at 150 °C remains 96% (x = 1.6) and 83% (x = 1.8) of the room-temperature values, respectively.

Innovate Designs for Upholstery Fabrics Glow in the Dark, Inspired from Islamic Art

This research concern on producing upholstery fabrics designs inspired from Islamic art which glowing in dark using strontium aluminate Phosphor. Photoluminescent (PL) material such as Phosphor of strontium aluminate (SrAl2O4: Eu2+, Dy3+) is a kind of energy storage material, it can absorb both ultraviolet (UV) and visible lights from the sunlight and keeps emitting light for a period of time in absence of the illumination source at a certain wave length. The research focused on Islamic art as a source of inspiration due to its richness in the floral, geometric, written, abstract and symbolic motifs. So that we use two pure cotton fabrics (100%) with different operational specifications, one of them (plain 1/1) and the other sample (Basket 3/3). These fabrics were used for producing the (PL) up holstery fabrics with seven different concentrations of strontium aluminate Phosphor (SAOED) pigment ranged from (1: 7 wt.%) using a hand printing method to produce fourteen samples. Our findings that there is a direct relationship between air permeability, bending length in weft & warp direction, tensile strength, elongation and the concentrations of (SAOED). The best sample performance evaluated by radar chart for the given properties is sample (A1) with the quality factor percentage (83.4%). According to the quality factor test result the research team decided applied the five innovate designs inspired from islamic art with the same specification of the sample which achieved a high functional property. The statistical analysis of the questionnaire results shows that the best design idea evaluated by radar chart (design two) with the quality factor percentage (86.4%). Therefore, using strontium aluminate Phosphor is considered a technological method that enriches the aesthetics and functional properties of the upholstery fabric design.

On the effects of milling and thermal regeneration on the luminescence properties of Eu2+ and Dy3+ doped strontium aluminate phosphors

This paper reports a comparison of luminescence, particle size and crystallinity reduction of SrAl2O4: Eu2+, Dy3+ (SA2) and Sr4Al14O25: Eu2+, Dy3+ (SA14) phosphors by ball milling. In addition, the regeneration possibilities of rare earth metal doped strontium aluminate phosphors (SAEDs) were investigated. The crystallinity degradation and particle size reduction were characterized by powder X-ray diffraction, and scanning electron microscopy (SEM) techniques respectively. Afterglow (AG), photo- (PL) and thermoluminescent (TL) properties of SAEDs were followed in parallel. The trap level shifts during the degradation and regeneration process were calculated from the TL data. The oxidation and reduction of Eu2+/3+ luminescence centre was followed by X-ray photoelectron spectroscopy (XPS). Luminescence degradation became significant after 2 μm avg. particle diameter reached, for both SAEDs. Considerable differences were found in their stress durabilities. The SA2 and SA14 characteristics are largely influenced by the details of the mechanical energy investment method, in reached crystallinity, particle diameter, and the Eu2+/3+ state, besides the total amount of energy transferred. The reversibility of the Eu2+/3+ ratio, PL and afterglow performance of the milled phosphors could be restored to some extent, by similar to synthesis annealing. The SA14 and SA2 phosphors responded differently to the regeneration process.

Electron life time (τ) in trap levels of Dy3+ activated calcium aluminate: Implications in TL dosimetry

RE3+ (Rare Earth) activated calcium aluminates (CaAl2O4) form an excellent class of phosphors for various applications. The multi-functionality of this class of phosphor is tailored by optimising the relative concentration of the trap-levels within the large band gap (Eg=7.4eV). In this paper we determine the trap-levels in Dy3+ activated nanocrystalline calcium aluminate (CaAl2O4: Dy3+) phosphor by rigorous analysis of the complex TL curves by computerised-glow-curve-deconvolution (CGCD) technique. We assume the kinetics to be the general order kinetic (1≤ b ≤ 2). Six trap levels have been identified with a lifetime ranging from 8 hours to 108 years at room temperature. The ones with τ300 = 6.46×1005 years, 1.02×1007 years and 9.02×1008 years in principle can be the candidates for TL dosimetric application.

Decomposition behavior and reaction mechanism of Ce0.67Tb0.33MgAl11O19 during Na2CO3 assisted roasting: Toward efficient recycling of Ce and Tb from waste phosphor

Waste aluminate phosphor is a valuable secondary resource of rare earth elements (REEs). However, Ce and Tb in aluminate green phosphor can hardly be extracted by direct leaching in an inorganic acid. Therefore, Na2CO3 assisted roasting is adopted to decompose the stable spinel structure of Ce0.67Tb0.33MgAl11O19 in the present work and to achieve the transformation of REEs to simple oxides. Based on the thermodynamic calculations, systematic experiments of thermal decomposition have been conducted. The thermal decomposition behavior, phase evolution, valence state change, variations in micro and macro morphology of the green phosphor during Na2CO3 assisted roasting were examined by using TG-DSC/MS, XRD, XPS, SEM/EDS analyses. The results indicated that the green phosphor began to react with solid Na2CO3 at 800 °C, and the reaction was dramatically accelerated with temperature rising above 851 °C. At about 1000 °C, Ce0.67Tb0.33MgAl11O19 could completely decomposed into CeO2, Tb2O3 and MgO by roasting in an equivalent mass of Na2CO3 for 2 h, while α-Al2O3 was hardly attacked in roasting. The decomposition mechanism of Ce0.67Tb0.33MgAl11O19 in molten Na2CO3 could be depicted by the unreacted shrinking core model, and the reaction rate constant was estimated at approximately nanometers per second. The synergistic effect of cation-oxoanion ensures the successful extraction of CeO2 and Tb2O3 from the green phosphor via Na2CO3 assisted roasting method. The converted CeO2 and Tb2O3 can be extracted by using chlorination roasting and separated from non-REE residues. According to these investigations, a new efficient process technology is proposed for sustainable recycling of waste phosphor.

High color stability white OLED with an exterior sandwiched color conversion layer

A sandwiched color conversion layer (CCL) was prepared on the exterior of a blue organic light-emitting diode (BOLED) to achieve white luminescence. Inorganic red aluminate phosphor was used for color conversion. To enhance optical outcoupling, light extraction layers (LELs) of microlens-like SiO2 scattering arrays (SO-LEL) and a roughed-glass diffuser (rG-LEL) were prepared. The addition of an SO-LEL led to a directional radiation of OLED. A light extraction and scattering model for optical transmission through the SO-LEL was developed. However, the rG-LEL caused a slight broadening in the electroluminescence spectrum. The sandwiched CCL had functions of color conversion, scattering, and light extraction. The white OLED with a sandwiched CCL exhibited directional emission and high color stability along with an optical outcoupling enhancement of 39% in power efficiency and 31% in external quantum efficiency.

Origin of long afterglow in strontium aluminate phosphors: Atomic scale imaging of rare earth dopant clustering

Ceramic pigments emitting long afterglow have enormous potential for emerging lighting applications that consume zero energy from the power grid. One of the most efficient compounds is strontium aluminate, when co-doped with 2 rare-earth elements — an optically active emitter, such as Eu 2+ , and an auxiliary ion, such as Dy 3+ — and B. To date, spectrophotometric methods are commonly used to determine the material structure supporting long afterglow, yielding indirect evidence of energy transfer between the rare-earth co-dopants. Here, atomic resolution HAADF-STEM imaging is used to resolve columns of Sr sub-lattice sites in the (012)-projection of a Sr 4 Al 14 O 25 :Eu,Dy single crystal. Through quantitative STEM image simulations, heavy rare earth dopants are shown to incorporate substitutionally into Sr sites, causing an enhancement in image contrast over that of neighboring atomic columns by 125%. DFT structural simulations demonstrate that Eu 2+ and Dy 3+ would incorporate into adjacent Sr lattice sites along the [012], enabling energy transfer between them that we see as afterglow. With the help of atomic resolution HAADF-STEM imaging, we also provide direct experimental evidence of clustering of ionic point defects induced by B doping, leading to extremely long (>14 h) afterglow in strontium aluminate phosphors.

Enhancing photoluminescence properties of Mn4+‐activated Sr4−xBaxAl14O25 red phosphors for plant cultivation LEDs

AbstractNon–rare earth Mn4+‐activated strontium aluminate phosphor is considered to be a promising material for plant cultivation field owing to their advantage of inexpensively, environment friendly, nontoxic, and appropriate spectral range. In this paper, a Sr4−xBaxAl13.99O25:0.01Mn4+,1.4H3BO3 strontium aluminate phosphor is synthesized by a convenient high‐temperature solid‐state reaction. The photoluminescence spectra located at red region with a peak at 655 nm in the range of 600 to 750 nm that can be excited under the excitation of ultraviolet (~346 nm) or blue light (~450 nm). The shape emission band at 655 nm is attributed to the transition of 2Eg‐4A2g. Furthermore, the emission intensity of Sr4−xBaxAl13.99O25: 0.01Mn4+,1.4H3BO3 phosphor is conducted in detail with the variety of Ba2+ doping concentration and the intensity can be enhanced to 140.9% than the Sr4Al13.99O25:0.01Mn4+,1.4H3BO3 when the value of Ba2+ concentration equal to 0.1 mol. In addition, the X‐ray diffraction spectra, element mapping, composition modifying, optical properties, FT‐IR spectra, diffuse reflectance spectra, thermal stability, and fluorescence lifetime are systematically investigated. According to the electro‐luminescent spectra of as‐packaged LED, indicating that the Sr3.9Ba0.1Al13.99O25:0.01Mn4+,1.4H3BO3 phosphor will become a great candidate for plant cultivation LEDs due to the emission spectra match well the plant pigment spectrum.

Preparation, structure, luminescence properties of terbium doped perovskite-like structure green-emitting phosphors SrLaAlO4:Tb3+

Rare earth aluminate phosphors are well-known for being nontoxic and environmentally friendly. In this work, Tb3+-doped SrLaAlO4 phosphors were synthesized via a facile high temperature solid-state reaction method. The Optimum reaction temperature is determined to be 1300 °C based on the results of powder X-ray diffraction (XRD). The SEM patterns and TEM images correspond with the results of Rietveld refinement and show that the SrLa1-xAlO4:xTb3+ samples present a flaky structure. The results of photoluminescence spectrums (PL) show that SrLa1-xAlO4:xTb3+ phosphors can absorb in the UV–vis spectral region of 228 nm–263 nm and exhibit several emission peaks between 450 and 650 nm, and the highest peak was at 508 nm. The luminescence properties of SrLa1-xAlO4:xTb3+ have a strict dependence on the cation substitution levels. When the doping concentration of Tb3+ was 0.05, the emission intensity of the sample is strongest. The thermal quenching result of the SrLa0.95AlO4:0.05 Tb3+ phosphors shows that these phosphors are relatively sensitive to temperature changes under an excitation of 228 nm, as the temperature increases from 25 °C to 125 °C, the emission intensity (peak at 548 nm) decayed to 55.11% of that at room temperature. However, when the temperature increases to 125 °C, the emission intensity (peak at 548 nm) decayed to 61.16% of the initial value under an excitation of 263 nm, which showed a relatively good thermal stability. The internal quantum efficiency (QE) values of the SrLa0.95AlO4:0.05 Tb3+ phosphors was measured and determined to be 48%. Under excitations of 228 nm and 263 nm, the lifetimes of the optimized sample SrLa0.95AlO4:0.05 Tb3+ were 1.3986 ms and 1.2095 ms, respectively, and the CIE coordinates of the sample were calculated as (0.2971, 0.4981), (0.3056, 0.5329), respectively. Under both excitations SrLa0.95AlO4:0.05 Tb3+ exhibited high-color-purity green emission.

Photocatalytic Properties of Strontium Aluminate Phosphors: A Review

Photocatalytic Properties of Strontium Aluminate Phosphors: A Review

Phase formation and luminescent properties of Сa12Al14O33:Eu, Nd prepared by sol–gel method

Сalcium aluminate Ca12Al14O33 and phosphors based on it were obtained using sol–gel technology. Complex studies were used to identify the dynamics of phase and structural transformations in the synthesis of Ca12Al14O33. The main stages of the calcium aluminate formation were determined using thermal analysis, IR spectroscopy and X-ray phase analysis. Solid-phase interaction in the formation of Ca12Al14O33 includes the steps of obtaining calcium carbonate and amorphous alumina (800 °C), aluminates of composition Ca3Al2O6 and CaAl2O4 (900–1000 °C), and Ca5Al6O14 and Ca4Al6O13 (1000–1100 °C). Ca12Al14O33 begins to form at 1100 °C. The graphic image of the structure was constructed according to the obtained atomic coordinates using the ReX Powder diffraction program. Luminescent properties of the phosphors of the composition Ca12−(0.05+x)Al14O33:NdxEu0.05 (x = 0.025–0.1) were investigated. It was determined that the highest intensity of luminescence is achieved at x = 0.05. With a further increase in the content of neodyum, there was a concentration quenching of the luminescence.

Enhance the luminescence properties of Ca14Al10Zn6O35:Ti4+ phosphor via cation vacancies engineering of Ca2+ and Zn2+

Ti4+-activated zinc calcium aluminate phosphors, owing to their excellent luminescence properties, nontoxicity, environment friendliness and low price, have a certain prospect in the field of plant cultivation. In this study, we have successfully synthesized a series of Ca14-yAl10-xZn6-zO35:xTi4+ (CAZO:Ti4+) phosphors through a high-temperature solid-state method. Furthermore, the emission spectrum of CAZO:Ti4+ located in bluish violet-emitting band, and has an emission peak at 378 nm upon the excitation of 268 nm due to the charge transfer of Ti4+-O2-. Moreover, the luminescence intensity of as-synthetized phosphors can be improved by cation vacancies engineering to compensate for charge unbalance. Especially, the luminescence intensity could be further improved when the Ca2+ vacancy is 0.35 mol or the Zn2+ vacancy is 0.275 mol. Furthermore, the X-ray powder diffraction (XRD) analysis and crystal structure are checked and confirmed that the synthesized material is pure phase. The concentration quenching mechanism, FT-IR spectra, UV–vis absorption properties, lifetimes and electron transition process of Ca14-yAl10-xZn6-zO35: xTi4+ were discussed in detail. From the above, the phosphor has a potential application for plant growth field due to its broad bluish violet emission.

Effects of co-activator species and transition metal ions doping on structure and fluorescence properties of strontium aluminate phosphors

The phosphors of SrAl2O4: Eu2+, RE3+ (RE = Dy3+, Tb3+, Ho3+, La3+, Nd3+, Y3+, Tm3+, Er3+) and SrAl2O4: Eu2+, Dy3+, M2+ (M = Mn2+, Ni2+, Mg2+, Cu2+, Zn2+) were synthesized by co-precipitation combined hydrothermal method, and analyzed by X-ray diffraction (XRD), fluorescence spectrometer and SEM. XRD patterns illustrated that the synthesized products all were the mixed crystal phase of SrAl2O4 and Sr4Al14O25. The diffraction peaks shapes of phosphors SrAl2O4: Eu2+, RE3+ (RE = Tb3+, Ho3+, Y3+) were almost unchanged contrast to the marked changes of phosphors SrAl2O4: Eu2+, RE3+ (RE = Tm3+, Er3+, Nd3+, La3+), which showed co-activator species had a great impact on the crystal field around the emission center (Eu2+). Besides, the peak positions of SrAl2O4: Eu2+, Dy3+, M2+ (M = Mn2+, Ni2+, Mg2+, Cu2+, Zn2+) were unaltered after doping, while the peak intensity of crystal phase Sr4Al14O25 was enhanced after doped by cations (Mn2+, Ni2+, Cu2+, Zn2+), which indicated the doping of transition metal ions would cause the crystal phase transition. The fluorescence analysis results indicated that the luminescent intensity were reduced after being doped by co-activator ions (Dy3+, Tb3+, Ho3+, La3+, Nd3+, Y3+), but enhanced when doped by co-activator ions (Tm3+, Er3+), and the final emission wavelength and intensity sequence were as follows: $$\lambda$$ Nd < $$\lambda$$ La < $$\lambda$$ Er < $$\lambda$$ Y < $$\lambda$$ Tm < $$\lambda$$ Tb < $$\lambda$$ Ho < $$\lambda$$ Dy, INd < IDy < IY < ITb < IHo < ILa < ITm < IEr. Instead, the fluorescence emission intensity decreased with the increment of the doping concentration of transition metal ions, which perhaps because the transition metal ions doping under the optimal concentration of co-activator could reduce the luminescence intensity of products due to the concentration quenching. The crystal particles of SrAl2O4: Eu2+, Dy3+ presented regular hexagon flake-like morphology with a width of ~ 500 nm and a thickness of ~ 70 nm. The title products could be applied in the safety indicators, emergency lighting danger signals, automobiles, solar cells, etc.

Synthesis and mechanoluminescent property of (Eu2+, Dy3+)-co-doped strontium aluminate phosphor by soft mechanochemistry-assisted solid-state method

(Eu2+, Dy3+)-co-doped strontium aluminate (SrAl2O4:Eu2+, Dy3+) powder as a mechanoluminescent (ML) phosphor was synthesized via soft mechanochemical pretreatment of precursor mixtures in a stirred media mill and subsequent calcination. Effect of soft mechanochemical pretreatment of precursors on the synthesis process as well as the photoluminescent (PL) and ML properties of SrAl2O4:Eu2+, Dy3+ phosphor was investigated. The precursor mixtures unground and ground at different time and the resultant phosphors were characterized by laser particle size analysis, X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy and optical property measurement. The results reveal that soft mechanochemical pretreatment of precursor mixture promotes the crystal growth, and reduces the subsequent calcination temperature. SrAl2O4:Eu2+, Dy3+ phosphor can be obtained via calcining at 1200 °C for precursor mixture ground at 60 min, but formed via calcining at 1400 °C for unground precursor mixture. The phosphor synthesized with precursor mixture ground at 60 min has the maximum PL and ML intensities due to the enhancement of Eu2+ and Dy3+ ions into the crystal lattice to form more electron traps. The measurements by a designed ML instrument indicate that the ML intensity increases with increasing impact stress, and decreases with multiple applications of the same impact stress on phosphor disks.

Sol-Gel Synthesis of Fluorescent Materials Based on Tricalcium Aluminate

Calcium aluminate Ca3Al2O6 and phosphors based on it were obtained by sol-gel method. Complex studies were used to identify the dynamics of phase and structural transformations in the synthesis of Ca3Al2O6. We used thermal analysis, IR spectroscopy, X-ray phase analysis, scanning electron microscopy and micro-X-ray spectral analysis. Solid-phase interaction in the formation of Ca3Al2O6 includes the steps of obtaining carbonate and calcium oxide at 700 °C, aluminates of composition Ca5Al6O14 (800 °C) and CaAl2O4 (900 °C). Ca3Al2O6 is formed at 850 °C, single-phase cubic calcium aluminate is formed at 1000 °C. The degree of formation of the particles is increased with increasing synthesis temperature. Using the method of adsorption of Gammet indicators we determined that the base Brensted centers predominate on the surface of calcium aluminate. The number of these centers decreases with an increase in the annealing temperature and with the introduction of the activator. The luminescent properties of the phosphors of the composition Ca3-xEuxAl2O6 (x = 0.01–0.1) were investigated by the method of spectrofluorimetry. The highest intensity of luminescence was achieved at x = 0.05. With a further increase in the content of europium, there was a concentration quenching of the luminescence.