Synthesis, luminescence and persistent luminescence of europium-doped strontium aluminates

Hagemann, Hans‐Rudolf; Afshani, Jafar

doi:10.1016/bs.hpcre.2021.06.001

Cited by 3 publications

(8 citation statements)

References 311 publications

(319 reference statements)

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“…Pure phase nanocrystals of SA 6 are obtained upon increasing the annealing temperature to 1150 °C. The phase diagram of the SrO–Al 2 O 3 system shows that SA 6 melts incongruently at the highest temperature among all strontium aluminate compounds (Figure S3), hinting at a high stability of the crystalline compound. Experimentally, the free energy of reaction between 1000 and 1300 K for the reactions SrO + 6Al 2 O 3 → SrAl 12 O 19 and SrO + 2Al 2 O 3 → SrAl 4 O 7 was found to be Δ G °/J mol –1 (±280) = −83386 – 25.744 ( T /K) and Δ G °/J mol –1 (±240) = −80187 – 25.376 ( T /K), respectively .…”

Section: Results and Discussionmentioning

confidence: 99%

“…The different distribution of the Sr 2+ and Al 3+ ions along the different facets in the crystal structure of SA 6 can contribute to the different facet growth rate as well. It is well-established that in the SrO–Al 2 O 3 system a higher Sr 2+ /Al 3+ ratio leads to a lower crystallization temperature Figure S7 shows the distribution of the ions along the (100), (010), and (001) facets.…”

Section: Results and Discussionmentioning

confidence: 99%

“…For instance, the afterglow properties of the long persistent phosphors such as SrAl 2 O 4 :Eu 2+ ,Dy 3+ are closely associated with the defects in their crystal structures acting as electron traps. 52,54 This compound shows remarkably superior afterglow emission when synthesized by a solid-state reaction than other synthesis methods. 54 In line with the importance of defects for the optical properties of a material, recently, a remarkably improved absorption was reported for ternary chalcogenide NPs through cation disorder engineering.…”

Section: ■ Introductionmentioning

confidence: 98%

“…Moreover, for SrO−Al 2 O 3 and similar systems, obtaining a pure crystalline phase is challenging due to the complex phase diagram. 52 On the other hand, optical properties of the dopant in these host crystals change dramatically from one phase to another. 53 Physical properties of the crystal (e.g., size and defects) play a crucial role as well.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Besides, precursor particles with homogeneous morphology and size distribution usually undergo aggregation during the HTA step, which severely limits the application of the crystals obtained by this method. Moreover, for SrO–Al 2 O 3 and similar systems, obtaining a pure crystalline phase is challenging due to the complex phase diagram . On the other hand, optical properties of the dopant in these host crystals change dramatically from one phase to another .…”

Section: Introductionmentioning

confidence: 99%

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Crystallization of SrAl₁₂O₁₉ Nanocrystals from Amorphous Submicrometer Particles

et al. 2022

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Advanced instrumentation and modern analysis tools such as transmission electron microscopy (TEM) have led to phenomenal progress in understanding crystallization, in particular from solution, which is a prerequisite for the design-based preparation of a target crystal. Nevertheless, little has been understood about the crystallization pathway under high-temperature annealing (HTA) conditions. Metal oxide crystals are prominent materials that are usually obtained via HTA. Despite the widespread application of hydro-/solvothermal methods on the laboratory scale, HTA is the preferred method in many industries for the mass production of metal oxide crystals. However, poor control over the morphology and grain sizes of these crystals under extreme HTA conditions limits their applications. Here, applying ex-situ TEM, the transformation of a single amorphous spherical submicrometer precursor particle of SrAl 12 O 19 (SA 6 ) at 1150 °C toward a nanosized thermodynamically favored hexagonal crystal is explored. It is illustrated in real space, step by step, how both kinetic and thermodynamic factors contribute to this faceting and morphology evolution. These results demonstrate a nonclassical nucleation and growth process consisting of densification, crystallite domain formation, oriented attachment, surface nucleation, 2-dimensional (2D) growth, and surface diffusion of the atoms to eventually result in the formation of a hexagonal platelet crystal. The TEM images further delineate a parent crystal driving the crystal lattice and morphological orientation of a network of interconnected platelets.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 98%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Crystallization of SrAl₁₂O₁₉ Nanocrystals from Amorphous Submicrometer Particles

et al. 2022

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Luminescence spectroscopy of CaAl12O19:Eu3+ and SrAl12O19:Eu3+ nanoparticles

Afshani

Delgado

Paveliuc

et al. 2022

Journal of Luminescence

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Defects and persistent luminescence in Eu-doped SrAl$_2$O$_4$

Hoang¹

2022

Preprint

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We investigate native point defects and rare-earth (co)dopants in SrAl2O4 using hybrid densityfunctional defect calculations. Europium (Eu) and dysprosium (Dy) are found to be mixed valence and energetically most favorable at the Sr lattice sites. However, unlike Eu where both Eu 2+ and Eu 3+ can be realized in synthesis, Dy is stable predominantly as Dy 3+ , and the divalent Dy 2+ may only be photogenerated under irradiation. On the basis of an analysis of Eu-related banddefect (including charge-transfer) and interconfigurational 5d-4f optical transitions, we assign the characteristic broad blue (445 nm) and green (520 nm) emission bands in Eu 2+ -doped SrAl2O4 to the 4f 6 5d 1 → 4f 7 transition in Eu 2+ incorporated at the Sr1 and Sr2 sites, respectively. Strontium interstitials (not oxygen vacancies, in contrast to what is commonly believed) and DySr can act as efficient electron traps for room-temperature persistent luminescence. This work calls for a reassessment of certain assumptions regarding specific carrier trapping centers made in all mechanisms previously proposed for the persistent luminescence in Eu-and (Eu,Dy)-doped SrAl2O4. It also serves as a methodological template for the understanding and design of rare-earth doped phosphors.

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Synthesis, luminescence and persistent luminescence of europium-doped strontium aluminates

Cited by 3 publications

References 311 publications

Crystallization of SrAl₁₂O₁₉ Nanocrystals from Amorphous Submicrometer Particles

Crystallization of SrAl₁₂O₁₉ Nanocrystals from Amorphous Submicrometer Particles

Luminescence spectroscopy of CaAl12O19:Eu3+ and SrAl12O19:Eu3+ nanoparticles

Defects and persistent luminescence in Eu-doped SrAl$_2$O$_4$

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Synthesis, luminescence and persistent luminescence of europium-doped strontium aluminates

Cited by 3 publications

References 311 publications

Crystallization of SrAl12O19 Nanocrystals from Amorphous Submicrometer Particles

Crystallization of SrAl12O19 Nanocrystals from Amorphous Submicrometer Particles

Luminescence spectroscopy of CaAl12O19:Eu3+ and SrAl12O19:Eu3+ nanoparticles

Defects and persistent luminescence in Eu-doped SrAl$_2$O$_4$

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Crystallization of SrAl₁₂O₁₉ Nanocrystals from Amorphous Submicrometer Particles

Crystallization of SrAl₁₂O₁₉ Nanocrystals from Amorphous Submicrometer Particles