Synthesis and characterization of CaAlxOy:Eu2+ phosphors prepared using solution-combustion method

Dejene, F.B.; Bem, D.B.; Swart, H.C.

doi:10.1016/s1002-0721(10)60380-8

Cited by 17 publications

(7 citation statements)

References 20 publications

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“…It is apparent that a good crystalline BaAl 2 O 4 powder could be obtained at lower temperature by liquid combustion process, which is lower than that required for the sol-gel method and the solid-state reaction method. Similar results were observed by our group for CaAl O :Eu 2+ persistent luminescence phosphors structural dependence on precursor compositions [16]. The luminescence spectra of BaAl O :Eu 2+ phosphors excited by UV light (λ = 325 nm) measured after removal of exposure source are shown in Fig.…”

Section: Resultssupporting

confidence: 88%

Synthesis and characterization of structural and luminescence properties of blue — green BaAlxOy:Eu2+ phosphor by solution — combustion method

Dejene

Kebede

2012

Open Physics

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Europium-doped barium aluminate (BaAlxOy:Eu2+) phosphors were obtained at low temperatures (500°C) using the solution — combustion of corresponding metal nitrate-urea solution mixtures. The particle size and morphology and the structural and luminescent properties of the synthesized phosphors were examined by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Electron diffraction spectroscopy (EDS) and photoluminescence (PL). It was found that the change in Ba: Al molar ratios showed greatly influence not only on the particle size and morphology, but also on their PL spectra and crystalline structure. The structure of BaAlxOy nanophosphors changes from a hexagonal Ba2Al10O17 phase for samples with 6:100 molar ratios to a hexagonal BaAl2O4 one with an increase in Ba content. The peak of the emission band occurs at a longer wavelength (around 615 nm) with a decrease in Ba concentration but displays a broad blue-green emission band composed from two emissions with the maximum at 495 and 530nm coming from Eu2+ in two sites for increasing Ba content. The blue-green emission is probably due to the influence of 5d electron states of Eu2+ in the crystal field because of atomic size variation causing crystal defects while the red emission is due to f - f transitions. These findings clearly demonstrate the possibility of fine tuning the colour emission.

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Section: Resultssupporting

confidence: 88%

Synthesis and characterization of structural and luminescence properties of blue — green BaAlxOy:Eu2+ phosphor by solution — combustion method

Dejene

Kebede

2012

Open Physics

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“…The decay curve is then decomposed into multiple (three or more) exponential components, [22][23][24][25] frequently called "fast," "slow," or "intermediate," however, the time constants obtained in this way are often difficult to interpret physically and the large number of parameters involved can make the fitting procedure unreliable.…”

Section: Continuous Trap Depth Distributionsmentioning

confidence: 99%

Revealing trap depth distributions in persistent phosphors

et al. 2013

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Persistent luminescence or afterglow is caused by a gradual release of charge carriers from trapping centers. The energy needed to release these charge carriers is determined by the trap depths. Knowledge of these trap depths is therefore crucial in the understanding of the persistent luminescence mechanism. Unfortunately, the trap depths in persistent phosphors are often difficult to evaluate in an accurate and reliable way. The existing analysis methods are mostly based on single experiments, or they ignore the possibility of a continuous distribution of trap depths. We present a procedure to accurately probe the activation energies, even in the presence of a continuous distribution of energy levels. By performing a series of thermoluminescence experiments with varying excitation duration and at varying excitation temperature, and employing the initial rise analysis method, the depth and shape of such a distribution can be estimated. As an example, we investigated the trap system in the violet persistent phosphor CaAl 2 O 4 :Eu,Nd, and show that it consists of a Gaussian-shaped distribution of trap depths. The maximal density of traps lies in the region around 0.9 eV, but the distribution extends to 0.7 eV on the shallow side and 1.2 eV on the deep side. The described procedure can be used to obtain a clear view of the trap system in other persistent phosphors as well. This can lead to a better understanding of the nature of these trapping centers, and the role they play in the persistent luminescent mechanism.

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“…For CaAl, multiple diffraction peaks can be observed. The diffractogram can best be described by the presence of CaAl x O y crystallites with variable stoichiometry, , alongside the crystalline γ-Al 2 O 3 phase. Multiple diffraction peaks can also be found in NaCAl.…”

Section: Resultsmentioning

confidence: 99%

Mid-temperature CO₂ Adsorption over Different Alkaline Sorbents Dispersed over Mesoporous Al₂O₃

Tsiotsias,

Georgiadis,

Charisiou

et al. 2024

ACS Omega

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CO 2 adsorbents comprising various alkaline sorption active phases supported on mesoporous Al 2 O 3 were prepared. The materials were tested regarding their CO 2 adsorption behavior in the mid-temperature range, i.e., around 300 °C, as well as characterized via XRD, N 2 physisorption, CO 2 -TPD and TEM. It was found that the Na 2 O sorption active phase supported on Al 2 O 3 (originated following NaNO 3 impregnation) led to the highest CO 2 adsorption capacity due to the presence of CO 2 -philic interfacial Al−O − −Na + sites, and the optimum active phase load was shown to be 12 wt % (0.22 Na/Al molar ratio). Additional adsorbents were prepared by dispersing Na 2 O over different metal oxide supports (ZrO 2 , TiO 2 , CeO 2 and SiO 2 ), showing an inferior performance than that of Na 2 O/Al 2 O 3 . The kinetics and thermodynamics of CO 2 adsorption were also investigated at various temperatures, showing that CO 2 adsorption over the best-performing Na 2 O/Al 2 O 3 material is exothermic and follows the Avrami model, while tests under varying CO 2 partial pressures revealed that the Langmuir isotherm best fits the adsorption data. Lastly, Na 2 O/Al 2 O 3 was tested under multiple CO 2 adsorption−desorption cycles at 300 and 500 °C, respectively. The material was found to maintain its CO 2 adsorption capacity with no detrimental effects on its nanostructure, porosity and surface basic sites, thereby rendering it suitable as a reversible CO 2 chemisorbent or as a support for the preparation of dual-function materials.

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Synthesis and characterization of CaAlxOy:Eu2+ phosphors prepared using solution-combustion method

Cited by 17 publications

References 20 publications

Synthesis and characterization of structural and luminescence properties of blue — green BaAlxOy:Eu2+ phosphor by solution — combustion method

Synthesis and characterization of structural and luminescence properties of blue — green BaAlxOy:Eu2+ phosphor by solution — combustion method

Revealing trap depth distributions in persistent phosphors

Mid-temperature CO₂ Adsorption over Different Alkaline Sorbents Dispersed over Mesoporous Al₂O₃

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Synthesis and characterization of CaAlxOy:Eu2+ phosphors prepared using solution-combustion method

Cited by 17 publications

References 20 publications

Synthesis and characterization of structural and luminescence properties of blue — green BaAlxOy:Eu2+ phosphor by solution — combustion method

Synthesis and characterization of structural and luminescence properties of blue — green BaAlxOy:Eu2+ phosphor by solution — combustion method

Revealing trap depth distributions in persistent phosphors

Mid-temperature CO2 Adsorption over Different Alkaline Sorbents Dispersed over Mesoporous Al2O3

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Mid-temperature CO₂ Adsorption over Different Alkaline Sorbents Dispersed over Mesoporous Al₂O₃