Study of Eu3+→Eu2+ reduction in BaAl2O4:Eu prepared in different gas atmospheres

Rezende, Marcos V. dos S.; Valério, Mário E.G.; Jackson, Robert A.

doi:10.1016/j.materresbull.2014.10.054

Cited by 29 publications

(16 citation statements)

References 24 publications

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“…When Eu 3+ ions are doped into the host and reduced to Eu 2+ ions, they will be surrounded by the framework structure of AlO 4 tetrahedron, which has considerable inhibitory effects on oxidation of Eu 2+ [34,35]. The framework consists of six-membered network structures formed by corner-shared AlO 4 tetrahedrons, whose centers are occupied by Eu 2+ ions working as the charge compensation cations.…”

Section: Self-reduction Of Eumentioning

confidence: 99%

Color tunable Ba0.79Al10.9O17.14:xEu phosphor prepared in air via valence state control

et al. 2017

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A series of luminescent Ba 0.79 Al 10.9 O 17.14 :xEu (x = 0.005-0.12) phosphors were prepared by high-temperature solid-state reaction in air atmosphere. The coexistence of Eu 2+ and Eu 3+ was observed and verified by photoluminescence (PL) and photoluminescence excitation (PLE) spectra, X-ray photoelectron spectra (XPS), and diffuse reflection spectra. The band emission peaking at 430 nm was assigned to 4F 6 5D-4F 7 transition of Eu 2+ , and another four emissions peaking at 589, 619, 655, and 704 nm were attributed to 4F-4F transitions of 5 D 0 -7 F J (J = 1, 2, 3, 4) of Eu 3+ . The related mechanism of self-reduction was discussed in detail. The color of the Ba 0.79 Al 10.9 O 17.14 :xEu phosphors could be shifted from blue (0.23, 0.10) to red (0.42, 0.27) by doping Li + ions, and the temperature dependence properties were investigated.

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Section: Self-reduction Of Eumentioning

confidence: 99%

Color tunable Ba0.79Al10.9O17.14:xEu phosphor prepared in air via valence state control

et al. 2017

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“…1−10 Other researchers emphasize the presence of interstitial oxygen useful for the reduction of europium during the heating of the material in hydrogen or ammonia. 7,11 Others applying this model maintain that the oxygen vacancies compete in the reduction process, where their presence is believed to stabilize the +3 oxidation state of europium. 12 Rezende et al studied Eu 3+ → Eu 2+ reduction in different gas atmospheres.…”

Section: Introductionmentioning

confidence: 99%

“…12 Rezende et al studied Eu 3+ → Eu 2+ reduction in different gas atmospheres. 11 So far, however, no one has studied how the chosen synthesis method influences reduction effectiveness.…”

Section: Introductionmentioning

confidence: 99%

Method to Measure the Degree of Reduction of Eu³⁺ to Eu²⁺: How Anion and Cation Vacancies Influence the Degree of Reduction

2021

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Phosphors for white light-emitting diode (LED) light sources are very often alkaline earth silicate matrices doped with Eu 2+ . As europium occurs in nature only in the +3 oxidation state, the synthesis of such phosphors requires annealing in a reducing atmosphere. Unfortunately, sometimes the reduction is not efficient. Therefore, it is necessary to precisely determine the reduction degree of Eu 3+ to Eu 2+ and to recognize all of the factors affecting the reduction process. This paper shows new insight into how defects such as calcium and oxygen vacancies affect the Eu 3+ → Eu 2+ reduction degree and the quantum efficiency of the Eu 2+ emission. This paper explains the mechanisms of reduction of Eu 3+ both in samples synthesized in sol−gel and solid state and the formation of defects and presents a method for identifying such defects using IR measurements. A useful method based on magnetic measurements to determine the degree of reduction of Eu 3+ is also presented. For this purpose, the åkermanite−gehlenite matrix was synthesized using two methods, solid-state and sol−gel. Annealing was carried out in two different atmospheres: vacuum and the H 2 /N 2 mixture. The samples produced by the solid-state method are free from calcium and oxygen vacancies, while those produced by the sol−gel method always have an abundance of them. The number of defects depends on the reducing atmosphere, stoichiometry, and the introduced codopants, either Li + or Zr 4+ ions. The results are universal and can be applied to other phosphors. The presented approach allows to develop a phosphor with high quantum efficiency.

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“… 6–8 In recent years, the reduction from Eu 3+ to Eu 2+ has been found to occur in the same crystal in an air atmosphere. For example, in aluminosilicates 9 , aluminate, 10,11 silicate, 12 phosphate, 13 borate, 14,15 the reduction from Eu 3+ to Eu 2+ have appeared. The Eu 2+ spectral position changes with the strength of the crystal field, and ultraviolet, blue, and red light are generated according to the degree of splitting.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and luminescence properties of novel Eu^2+/3+, Ce³⁺ ion single- and co-doped BaZn₂(PO₄)₂ phosphors for white-light applications

Zhu

Wang

et al. 2019

RSC Adv.

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Study of Eu3+→Eu2+ reduction in BaAl2O4:Eu prepared in different gas atmospheres

Abstract: and that only some of the Eu ions can be stabilized in the divalent state. A model of Eu reduction process, based on the incorporation of charge compensation defects, is proposed.

Cited by 29 publications

References 24 publications

Color tunable Ba0.79Al10.9O17.14:xEu phosphor prepared in air via valence state control

Color tunable Ba0.79Al10.9O17.14:xEu phosphor prepared in air via valence state control

Method to Measure the Degree of Reduction of Eu³⁺ to Eu²⁺: How Anion and Cation Vacancies Influence the Degree of Reduction

Synthesis and luminescence properties of novel Eu^2+/3+, Ce³⁺ ion single- and co-doped BaZn₂(PO₄)₂ phosphors for white-light applications

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Study of Eu3+→Eu2+ reduction in BaAl2O4:Eu prepared in different gas atmospheres

Abstract: and that only some of the Eu ions can be stabilized in the divalent state. A model of Eu reduction process, based on the incorporation of charge compensation defects, is proposed.

Cited by 29 publications

References 24 publications

Color tunable Ba0.79Al10.9O17.14:xEu phosphor prepared in air via valence state control

Color tunable Ba0.79Al10.9O17.14:xEu phosphor prepared in air via valence state control

Method to Measure the Degree of Reduction of Eu3+ to Eu2+: How Anion and Cation Vacancies Influence the Degree of Reduction

Synthesis and luminescence properties of novel Eu2+/3+, Ce3+ ion single- and co-doped BaZn2(PO4)2 phosphors for white-light applications

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Method to Measure the Degree of Reduction of Eu³⁺ to Eu²⁺: How Anion and Cation Vacancies Influence the Degree of Reduction

Synthesis and luminescence properties of novel Eu^2+/3+, Ce³⁺ ion single- and co-doped BaZn₂(PO₄)₂ phosphors for white-light applications