Fine-sized BaMgAl10O17:Eu2+ phosphor powders prepared by spray pyrolysis from the spray solution with BaF2 flux

doi:10.1016/j.ceramint.2009.03.004

Ceramics International

Volume 35, Issue 7, September 2009, Pages 2651-2657

https://doi.org/10.1016/j.ceramint.2009.03.004 Get rights and content

Abstract

Fine-sized BaMgAl₁₀O₁₇:Eu²⁺ phosphor powders with plate-like morphology were prepared by spray pyrolysis process. The effects of ratio of BaF₂ and Ba(NO₃)₂ used as the source materials of Ba component on the morphological and optical properties of the BaMgAl₁₀O₁₇:Eu²⁺ phosphor powders were investigated. BaF₂ was used as the flux material as well as the source material of Ba component. The phosphor powders prepared from the spray solution with the same mole concentrations of BaF₂ and Ba(NO₃)₂ had fine size, plate-like morphology and narrow size distribution. The addition of BaF₂ as the source material of Ba component increased the photoluminescence intensities of the phosphor powders. The phosphor powders prepared from the spray solution with the ratios of BaF₂ and Ba(NO₃)₂ larger than 1 had the similar photoluminescence intensities to that of the commercial product.

Introduction

BaMgAl₁₀O₁₇:Eu²⁺(BAM:Eu) phosphor, which has plate-like structure in conventional preparation methods, is an important blue-emitting phosphor for plasma display panels (PDPs) and fluorescent lamps [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. The phosphor powders with fine size and regular morphology are required to obtain the good phosphor layer with low thickness for high definition PDPs. BAM:Eu phosphor powders with high photoluminescence intensities under ultraviolet and vacuum ultraviolet should be post-treated at high temperatures above 1500 °C under reducing atmosphere. Flux materials, such as AlF₃ and BaF₂, were applied in the solid-state reaction method to reduce the preparation temperature of the BAM:Eu phosphor powders.

Flux materials were also applied to the preparation of phosphor powders by spray pyrolysis. Flux materials dissolved to the spray solution were effective in improving the brightness of the phosphor powders by eliminating the surface defects of the powders [11], [12], [13]. In the previous paper, the AlF₃ flux material insoluble in distilled water was applied in the preparation of blue-emitting BAM:Eu phosphor powders by the spray pyrolysis [14]. The precursor powders prepared by spray pyrolysis from the spray solution without flux material were reacted with AlF₃ flux by solid-state reaction method. AlF₃ flux improved the morphological and optical properties of the BAM:Eu phosphor powders.

In this study, fine-sized BAM:Eu phosphor powders with plate-like morphology were prepared by spray pyrolysis process from the spray solution with flux material. The effects of ratio of BaF₂ and Ba(NO₃)₂ used as the source materials of Ba component on the morphological and optical properties of the BAM:Eu phosphor powders were investigated. BaF₂ was used as the flux material as well as the source material of Ba component.

Section snippets

Experiment

The BAM:Eu precursor powders were prepared by ultrasonic spray pyrolysis from the spray solutions with BaF₂ and Ba(NO₃)₂. The ultrasonic spray pyrolysis system has a droplet generator, a quartz reactor, and a powder collector. A 1.7 MHz ultrasonic spray generator with six resonators is used to generate large amount of droplets. The length and diameter of the quartz reactor are 1200 and 50 mm, respectively. The flow rate of the air used as the carrier gas was 30 L/min. The preparation temperature

Results and discussion

The effect of BaF₂ flux on the optical properties of the BAM:Eu phosphor powders prepared by spray pyrolysis was investigated as the previous study. Small amount of BaF₂ added to the spray solution with stoichiometric composition of BAM:Eu phosphor did not improve the optical characteristics of the phosphor powders. Therefore, in this study, the amount of Ba component dissolved to the spray solution was maintained to the stoichiometric composition of BAM:Eu phosphor. Fig. 1 shows the SEM images

Conclusions

The BAM:Eu phosphor powders were prepared by spray pyrolysis process from the spray solutions with the various ratios of BaF₂ and Ba(NO₃)₂. BAM:Eu phosphor powders prepared from the spray solutions with appropriate BaF₂ contents had regular morphologies, fine sizes and narrow size distributions. Addition of BaF₂ improved the photoluminescence intensities of the BAM:Eu phosphor powders. The phosphor powders with the maximum photoluminescence intensity was obtained from the spray solution with

References (14)

K. Yokota et al.
Eu²⁺-activated barium magnesium aluminate phosphor for plasma displays—phase relation and mechanism of thermal degradation
J. Lumin.
(2001)
K.C. Mishra et al.
A scattered wave model of electronic structure of Eu²⁺ in BaMgAl₁₀O₁₇ and associated excitation processes
J. Lumin.
(2002)
K.Y. Jung et al.
Improved thermal resistance of spherical BaMgAl₁₀O₁₇:Eu blue phosphor prepared by spray pyrolysis
J. Lumin.
(2005)
Y. Zhou et al.
Morphology control and luminescence properties of BaMgAl₁₀O₁₇:Eu²⁺ phosphors prepared by spray pyrolysis
J. Solid State Chem.
(2005)
D.S. Jung et al.
Gd₂O₃:Eu phosphor particles prepared from spray solution containing boric acid flux and polymeric precursor by spray pyrolysis
Opt. Mater.
(2006)
D.S. Jung et al.
Effect of boric acid flux on the characteristics of (CeTb)MgAl₁₁O₁₉ phosphor particles prepared by spray pyrolysis
J. Alloys Compd.
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Use of LiCl flux in the preparation of Y₂O₃:Eu phosphor particles by spray pyrolysis
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There are more references available in the full text version of this article.

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Broadening the excitation spectrum of BaMgAl<inf>10</inf>O<inf>17</inf>:Cr3+ using Eu2+ as a codopant
2022, Journal of Luminescence
Citation Excerpt :
Over the period of long history of these phosphors, a variety of methods aiming at simpler procedures have been employed. These include use of precursors which decompose and react at lower tempertures [42], decomposition of metal complex [43], citrate complex method [44], nano-coating method [45], sputtering [46], radio frequency sputtering [47], aerosol flame deposition [48], polymeric gel deflagration [49], Aerosol Pyrolysis [50], spray pyrolysis [51], flux-assisted spray pyrolysis [52], flame spray pyrolysis [53], atomic layer deposition (ALD) [54], Microwave synthesis [55], microwave irradiation technique [56], hydrothermal synthesis [57]. Ingenious tricks have been used for simplifying the synthesis.
BAM:Eu is a very well known, commercial phosphor that is used for tricolor fluorescent lamps and plasma display panels. In recent years, Cr³⁺ doped BAM had been suggested as a phosphor for LED lamps for plant growth. However, excitation spectrum of Cr³⁺ is narrow. To overcome this problem, we have attempted co-doping by Eu²⁺. Eu²⁺ → Cr³⁺ energy transfer was observed in BaMgAl₁₀O₁₇:Eu²⁺,Cr³⁺ phosphor. The energy transfer was established by photoluminescence emission, excitation and lifetime measurements. Efficiency of the energy transfer is 40.2%. By virtue of this energy transfer, the excitation spectrum corresponding to Cr³⁺ emission covers a broad spectral region 340–430 nm. These phosphors were prepared by facile combustion synthesis which is a fast method. It is suggested that this phosphor will be useful for preparing LED lamps based on near ultraviolet, violet and blue chips.
Photoluminescence properties of Ca-doped BaMgAl<inf>10</inf>O<inf>17</inf>:Eu2+,Mn2+ blue phosphor using BaF<inf>2</inf> and CaF<inf>2</inf> as co-flux
2014, Journal of Rare Earths
Ca-doped BaMgAl₁₀O₁₇:Eu²⁺,Mn²⁺ (BAM) blue phosphors were synthesized by flux assisted solid-state reaction method using CaF₂ and BaF₂ as co-flux. Good dispersity and particle size homogenization of hexagonal pure phase BAM were obtained by sintering at 1400 °C. The effects of the Ca²⁺ ions content on the structure, morphology and photoluminescence properties of the phosphors were studied. The results indicated that the incorporation of Ca could decrease the lattice constant, improve the homogeneity and dispersity and enhance the photoluminescence (PL) intensity of the phosphor effectively. The optimum Ba_0.86Ca_0.04Mg_0.97Al₁₀O₁₇:0.1Eu²⁺,0.03Mn²⁺ PL intensity was enhanced for about 30% and relative brightness was improved about 4%. Furthermore, the synthesized BAM and commercial BAM phosphors were annealed for 30 min at 600 °C in air. The Ca-doped phosphors had stronger emission intensity, higher brightness and better chromaticity stability than that of the commercial phosphor. These results indicated that Ca-doped blue phosphors had good potential applications in the commercial tricolor fluorescent lamps as well as in other display and lamps.
A structural approach of the flux effect on blue phosphor BAM:Eu (BaMgAl<inf>10</inf>O<inf>17</inf>:Eu2+)
2013, Materials Research Bulletin
Citation Excerpt :
Another major topic associated to BAM:Eu2+ is the oxidation of Eu2+ into Eu3+ during the final elaboration process of the fluorescent devices, which takes place around 600 °C under air [1], or during the use. Adding a flux to the phosphor before the thermal treatment [2–6] is generally considered as an efficient way to address the above mentioned issues, as the re-crystallization by this mineral compound allows an homogeneous distribution of the dopant and reduces its oxidation by modifying the microstructure of the material. Nevertheless, the progresses in this domain are based upon empirical observations rather than phenomenological studies.
In the aim of understanding the relations between the spectroscopic properties of blue phosphor BaMgAl₁₀O₁₇:Eu²⁺ and its crystal structure, microstructure and chemical composition, three fluoride fluxes (LiF, MgF₂ and NH₄F) have been added before final thermal treatment and their effect analyzed. LiF changes the polycrystalline and spherical grains into hexagonal platelets without significant cations exchange and improves the luminescence. NH₄F and MgF₂ only have a limited effect, the former because of its low point of decomposition, the latter because of the formation of spurious MgAl₂O₄ that reduces the luminescence. In a general way, re-crystallization results in variations of the dopant distribution between the three host sites of the structure. Chromaticity is only faintly affected, but important variations of the absorption and excitation spectra are observed, allowing a strong increase of photoluminescence intensity under near-UV excitation.
Structural, morphological and optical investigations on BaMgAl <inf>10</inf>O<inf>17</inf>:Eu2+ elaborated by a microwave induced solution combustion synthesis
2011, Materials Research Bulletin
Citation Excerpt :
It leads to big size range and irregular shapes, inappropriate for the devices foreseen [8,9,16]. To compensate for these drawbacks, alternative preparation techniques have been developed such as sol–gel process [10,17–21], hydrothermal synthesis [22], co-precipitation [23], homogeneous precipitation [24], spray pyrolysis [25] and combustion synthesis [22,26–31]. Solution combustion synthesis (SCS) is a wet-chemical synthesis which does not require further calcinations and can produce well-crystallized oxides within a short duration from cheap precursors (nitrates and an organic fuel).
Blue-emitting Eu²⁺-doped barium magnesium aluminate (BaMgAl₁₀O₁₇:Eu²⁺) for advanced displays and lighting devices was prepared by a microwave induced solution combustion synthesis using urea as combustion fuel and nitrates as oxidizer. Purity control of as-synthesized blue phosphor particles was undertaken by modifying the fuel to oxidizer molar ratio. X-ray diffraction, scanning electron microscopy and photoluminescence were used to investigate powders crystallinity, particles size, morphology and luminescent properties, respectively. Fuel-rich urea reactions preferentially lead to pure phases compared to the powders synthesized with a stoichiometric fuel to oxidizer ratio. In both cases, we produce a nearly pure well-crystallized and nanostructured BaMgAl₁₀O₁₇:Eu²⁺. Photoluminescence measurements exhibit the characteristic blue emission of Eu²⁺ under UV light excitation however a weak red emission associated to Eu³⁺ is also detected.
Preparation of BaMgAl<inf>10</inf>O<inf>17</inf>:Eu2+ phosphor with small particle size by co-precipitation method
2011, Journal of Alloys and Compounds
Citation Excerpt :
Optimal phosphor particles should have a particle size of 1–2 μm [8,9], be well-crystallized (preferably single crystal particles), and have a good dispersion in the slurry. New synthesis methods have been developed in recent years to reduce the particle size of the aluminate phosphors and also to improve the particle morphology [10–25]. Sol–gel technique was introduced to obtain fine phosphor particles; Wang et al. prepared BAM nanorods by this method [11].
A BaMgAl₁₀O₁₇:Eu²⁺ phosphor with fine particle size was synthesized by a chemical co-precipitation method. Co-precipitation of Ba²⁺, Al³⁺, Mg²⁺, and Eu²⁺ was achieved under precisely controlled precipitation conditions. The Al³⁺ ions were precipitated as ammonium aluminum carbonate hydroxide (AACH). Phase transition and particle growth processes of the precipitate mixture during calcining process were investigated, and the formation mechanism of the BaMgAl₁₀O₁₇ phase was discussed. The results show that the formation temperature of the BaMgAl₁₀O₁₇ phase in the co-precipitation mixture was significantly lower than that of a high temperature solid state reaction method. The BaMgAl₁₀O₁₇ phase was formed from the reaction between the BaAl₂O₄ phase and γ-Al₂O₃ phase; no α-Al₂O₃ phase appeared during the entire process. Well-dispersed BaMgAl₁₀O₁₇:Eu²⁺ phosphor powder in the form of hexagonal flakes with small particle size (1–2 μm) could be prepared by this method.
Luminescent Materials Based on Aluminates: A Review
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Ceramics International

Abstract

Introduction

Section snippets

Experiment

Results and discussion

Conclusions

References (14)

Eu²⁺-activated barium magnesium aluminate phosphor for plasma displays—phase relation and mechanism of thermal degradation

J. Lumin.

A scattered wave model of electronic structure of Eu²⁺ in BaMgAl₁₀O₁₇ and associated excitation processes

J. Lumin.

Improved thermal resistance of spherical BaMgAl₁₀O₁₇:Eu blue phosphor prepared by spray pyrolysis

J. Lumin.

Morphology control and luminescence properties of BaMgAl₁₀O₁₇:Eu²⁺ phosphors prepared by spray pyrolysis

J. Solid State Chem.

Gd₂O₃:Eu phosphor particles prepared from spray solution containing boric acid flux and polymeric precursor by spray pyrolysis

Opt. Mater.

Effect of boric acid flux on the characteristics of (CeTb)MgAl₁₁O₁₉ phosphor particles prepared by spray pyrolysis

J. Alloys Compd.

Use of LiCl flux in the preparation of Y₂O₃:Eu phosphor particles by spray pyrolysis

J. Eur. Ceram. Soc.

Cited by (11)

Broadening the excitation spectrum of BaMgAl<inf>10</inf>O<inf>17</inf>:Cr<sup>3+</sup> using Eu<sup>2+</sup> as a codopant

Photoluminescence properties of Ca-doped BaMgAl<inf>10</inf>O<inf>17</inf>:Eu<sup>2+</sup>,Mn<sup>2+</sup> blue phosphor using BaF<inf>2</inf> and CaF<inf>2</inf> as co-flux

A structural approach of the flux effect on blue phosphor BAM:Eu (BaMgAl<inf>10</inf>O<inf>17</inf>:Eu<sup>2+</sup>)

Structural, morphological and optical investigations on BaMgAl <inf>10</inf>O<inf>17</inf>:Eu<sup>2+</sup> elaborated by a microwave induced solution combustion synthesis

Preparation of BaMgAl<inf>10</inf>O<inf>17</inf>:Eu<sup>2+</sup> phosphor with small particle size by co-precipitation method

Luminescent Materials Based on Aluminates: A Review