Effect of microwave irradiation on surface characteristics and luminescent properties of BaMgAl10O17:Eu blue phosphor

doi:10.1016/j.jpcs.2007.11.026

Journal of Physics and Chemistry of Solids

Volume 69, Issues 2–3, February–March 2008, Pages 362-365

https://doi.org/10.1016/j.jpcs.2007.11.026 Get rights and content

Abstract

BaMgAl₁₀O₁₇:Eu (BAM) has been an excellent blue-emitting phosphor due to its outstanding luminescence efficiency and purity for plasma display panels. An attempt of employing microwave irradiation to modify the surface properties including morphology and crystallinity of BAM powder was performed in this work. X-ray powder diffraction (XRD) analysis and scanning electron microscopy (SEM) images show that the blue-emitting phosphors after microwave irradiation treatment exhibit better crystallinity and smoother surface. Furthermore, the vacuum ultraviolet photoluminescence spectra show that the luminescent intensity of BAM phosphors can be effectively enhanced by a factor of six times under microwave irradiation treatment. The enhanced luminescent properties can be closely related to the surface modification and reduced defects of the BAM blue-emitting phosphors.

Introduction

AC color plasma display panels (PDPs) have been well-recognized as the most promising candidates for large-sized flat panel displays (FPD). However, the performance of phosphor luminance including brightness, color purity, stability and efficiency in PDPs has been still unsatisfactory compared to CRT displays [1]. To overcome this disadvantage, a new generation of large-area display panel with an efficient illuminating technology has been of critical concern. Illuminating phosphors are the key materials to improve the performance of PDPs such as brightness, cost-effectiveness and stability [2], [3]. So far, red-emitting (Y,Gd)BO₃:Eu (YGB), blue-emitting BaMgAl₁₀O₁₇:Eu (BAM), green-emitting Zn₂SiO₄:Mn (ZSM) have been mostly used as illuminating phosphors. However, BAM phosphor has been paid attention because of low brightness (blue), severe degradation of luminescence intensity and a color shift toward longer wavelength [4], [5], [6]. Several factors such as crystallinity, particle size and shape, and surface morphology have been considered and adopted to improve the luminance efficiency of BAM and the lifetime of PDPs [7], [8], [9], [10]. In addition, microwave irradiation treatment was also developed as a new tool for high-temperature processing of materials because it can give rapid and uniform heating, improved physical and mechanical properties [11]. Even so, microwave irradiation has been little applied to modify the optical behavior of phosphors.

Therefore, in this work, a simple microwave irradiation treatment was used for surface modification of the BAM powder. As surprisingly discovered, a considerable change in the morphological geometry of the phosphor powder was observed. Effect on physical character and resulting illuminant properties of the BAM phosphor will be investigated and discussed.

Section snippets

Experiment

To study the effect of microwave irradiation on the luminescent efficiency of PDP phosphor powders, commercial blue-emitting BaMgAl₁₀O₁₇:Eu²⁺ (BAM) powder was used as model phosphor which was purchased from Kasei (Serial no. KX-501A; d=3.8 g/cm³, D₅₀=2.7 μm, and fabricated by solid-state method). Prior to experiment, the powders were stored in nitrogen environment to prevent influence from mist or hydroxyl. A domestic MW system (2000 W, 2.45 GHz) was modified by installing a condenser through a

Results and discussion

Fig. 1 shows the particle morphology of the phosphor powder before and after microwave treatment. Without microwave irradiation, the blue-light phosphor presents platelets with particle size ranging from 2 to 5 μm as shown in Fig. 1(a). However, when the phosphors were treated by microwave irradiation, all the morphological changes of blue-light phosphor are at the edges which may be round due to heating or diffusion but their size remained almost unchanged as shown in Fig. 1(b)–(d). The change

Conclusion

Blue-light phosphors with improved luminescence property can be obtained through microwave irradiation. Surface morphology of the phosphor particles is extensively modified, permitting better crystallinity and particle density to be developed. The PL property shows that the luminescent efficiency of the phosphors can be improved by a factor of six times under microwave irradiation. To the best of our knowledge, this is the first technical report in the community. These results indicate that a

Acknowledgment

The authors gratefully acknowledge the financial support of Central Research Institute, Chungwha Picture Tubes, Ltd., Taoyuan, Taiwan, ROC.

References (15)

C.R. Ronda
J. Lumin.
(1997)
K.-G. Lee et al.
Solid State Commun.
(2002)
E. van der Kolk et al.
J. Lumin.
(2000)
K. Yokota et al.
J. Lumin.
(2001)
T.S. Copeland et al.
J. Lumin.
(2002)
S.B. Park et al.
J. Mater. Sci.: Mater. Electron.
(2003)
D.E. Clark et al.
Mater. Sci. Eng. A
(2000)

There are more references available in the full text version of this article.

Cited by (12)

Tm3+→Tb3+ energy transfer induced color-tunable in double-doped LiLaSiO<inf>4</inf> phosphors
2021, Journal of Luminescence
Citation Excerpt :
Used the microwave radiation method to crystallize the amorphous La0·7Sr0·3MnO3 and La0·7Ca0·3MnO3 precursor powder in only 60 s. Compared with the traditional method, the high-temperature 800 °C crystallized 2 h, it not only shortens the time, improves efficiency, but also avoids the high-temperature sintering. Kuo et al. [35]. Synthesized BaMgAl10O17: Eu phosphor by microwave radiation.
In this paper, a series of color-tunable LiLaSiO₄:βTm³⁺, γTb³⁺ phosphors were quickly synthesized by microwave-assisted solid-phase reaction method. Under proper ultraviolet light excitation, Tm³⁺ ions produce ¹D₂→³F₄ energy level transition and emit blue light, and the concentration quenching point is β = 1.5%mol. The color coordinates are (0.139, 0.046), compared with commercial blue phosphors. It has a higher color purity and color saturation. The Tb³⁺ ions produce ⁵D₄→⁷F₅ energy level transition and emit green light, and the color coordinate is (0.324, 0.508). In Tm3+-Tb3+ double-doped LiLaSiO₄ phosphors, the concentration quenching point of Tb³⁺ ions is γ = 6%mol. By characterizing the fluorescence lifetime and the luminous intensity of the Tm³⁺-Tb³⁺ co-doped LiLaSiO₄ phosphor, it is verified that there is an energy transfer of Tm³⁺→Tb³⁺ in the phosphor. The energy transfer efficiency and energy transfer mechanism have been investigated in detail. From the researched luminous properties, it is found that Tm³⁺-Tb³⁺ co-doped LiLaSiO₄ phosphor is an ideal material for light-emitting diodes, luminescent materials and fluorescent display devices.
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.
Luminous characteristics and thermal stability of BaMgAl<inf>10</inf>O<inf>17</inf>:Eu2+ phosphor for white light-emitting diodes
2010, Physica B: Condensed Matter
A blue-emitting phosphor, BaMgAl₁₀O₁₇:Eu²⁺ (BAM) was prepared by the solid-state reaction and X-ray powder diffraction (XRD) analysis confirmed the formation of BAM. Photoluminescence (PL) results showed that the phosphor can be efficiently excited by the light from near ultraviolet (NUV) to visible, and exhibited bright blue emission. The effect of the doped-Eu²⁺ in BAM on the PL was investigated. To improve the BAM's thermal stability, BAM doped with additional Mg²⁺ was studied. The experiment results showed that additional 0.05 mol Mg²⁺-doped BAM had the highest emission intensity and thermal stability. By combining with NUV LED chip (GaN-based 380 nm emitting), a novel intense white LED was fabricated based on the blue phosphor BAM and a red phosphor Ca(La_0.5Eu_0.5)₄Si₃O₁₃. The white LED has the characteristics of color-rendering index of 87, CIE chromaticity coordinates (x, y) of (0.3225, 0.3187), color temperature Tc of 5680 K, and light output of 51.7 lm/W under the forward-bias current of 20 mA. As the current increases, the relative intensity increases, the correlated color temperature Tc increases from 4000 to 7900 K and the color-rendering index Ra increases from 83 to 91 simultaneously.
A novel blue-emitting Ca<inf>2</inf>B<inf>5</inf>O<inf>9</inf>Br:Eu2+ phosphor prepared by a microwave calcination route
2010, Materials Chemistry and Physics
A blue-emitting Ca₂B₅O₉Br:Eu²⁺ phosphor for white light-emitting diodes was synthesized via a microwave calcination route. The phosphor powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer, respectively. The obtained results revealed that the Ca₂B₅O₉Br:Eu²⁺ phosphor prepared by the microwave calcination route possessed a rod-like morphology with the single phase orthorhombic structure. Based on the photoluminescence analysis, it was found that Ca₂B₅O₉Br:Eu²⁺ phosphor exhibited a broad excitation band chiefly in the near ultraviolet region (270–420 nm) and a blue broad emission band of main peak at 452 nm under the strongest excitation of 411 nm. Further investigation on concentration-dependent emission spectra indicated that Ca₂B₅O₉Br:0.03Eu²⁺ phosphor exhibited the strongest luminescent intensity, and the concentration quenching for the two Eu-site emission centers was caused by dipole–dipole interactions.
Preparation and tunable luminescence of microcrystalline SrMg<inf>2</inf>Al<inf>16</inf>O<inf>27</inf>:Tb3+ and Eu3+ phosphor for solid state lighting
2017, Journal of Materials Science: Materials in Electronics
Novel blue-emitting SrMg<inf>2</inf>Al<inf>16</inf>O<inf>27</inf>:Eu 2+ phosphor for solid-state lighting
2011, Luminescence

View all citing articles on Scopus

View full text

Article preview

Journal of Physics and Chemistry of Solids

Abstract

Introduction

Section snippets

Experiment

Results and discussion

Conclusion

Acknowledgment

References (15)

J. Lumin.

Solid State Commun.

J. Lumin.

J. Lumin.

J. Lumin.

J. Mater. Sci.: Mater. Electron.

Mater. Sci. Eng. A

Cited by (12)

Tm<sup>3+</sup>→Tb<sup>3+</sup> energy transfer induced color-tunable in double-doped LiLaSiO<inf>4</inf> phosphors

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

Luminous characteristics and thermal stability of BaMgAl<inf>10</inf>O<inf>17</inf>:Eu<sup>2+</sup> phosphor for white light-emitting diodes

A novel blue-emitting Ca<inf>2</inf>B<inf>5</inf>O<inf>9</inf>Br:Eu<sup>2+</sup> phosphor prepared by a microwave calcination route

Preparation and tunable luminescence of microcrystalline SrMg<inf>2</inf>Al<inf>16</inf>O<inf>27</inf>:Tb<sup>3+</sup> and Eu<sup>3+</sup> phosphor for solid state lighting

Novel blue-emitting SrMg<inf>2</inf>Al<inf>16</inf>O<inf>27</inf>:Eu <sup>2+</sup> phosphor for solid-state lighting