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MATERIALS RESEARCH

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Preparation of nonaggregated Y2 O3 : Eu phosphor particles by spray pyrolysis method Yun Chan Kanga) Department of Chemical Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan

Seung Bin Park Department of Chemical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong-gu, Taejon 305-701 Korea

I. Wuled Lenggoro and Kikuo Okuyamab) Department of Chemical Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan (Received 10 July 1998; accepted 27 January 1999)

Y2 O3 : Eu phosphor particles were directly prepared by a spray pyrolysis method. Photoluminescence, morphology, and crystallinity of the as-prepared particles were investigated. The as-prepared particles above 600 ±C had good crystallinity, and the crystallinity increased with increasing reactor temperatures. The particles had spherical morphology and were nonaggregated. The mean size of the particles increased from 0.34 to 1.2 mm when the solution concentration was increased from 0.03 to 1 M. The as-prepared particles had good red emission without annealing at high temperatures when excited with uv light. The main emission peak was 612 nm. The brightness of the as-prepared particles increased with increasing temperatures because of good activation and crystallization at high temperatures.

I. INTRODUCTION

Rare-earth-doped oxide particles have been widely studied for application of displays such as high definition (HD), projection televisions (PTVs), and flat panel displays (FPDs). Phosphor materials must have a narrow size distribution, nonagglomeration, and characteristics and spherical morphology for good luminescent characteristics. The mean size of the particles is very important for high resolution and high efficiency.1,2 Also the small particles can improve on aging by forming a densely packed phosphor layer. It has been predicted that optimum phosphor characteristics will be particle sizes on the order of 1 mm. Spherical morphology is also required for high brightness and high resolution. If the phosphor particles have a spherical shape, scattering of light evolved from the phosphors decreases. Additionally, high packing densities can be obtained by using spherical phosphors. Eu-doped Y2 O3 particles are well-known as a good red phosphor for applications in displays and lamps.1–8 Conventionally, Y2 O3 : Eu particles are prepared by a solid state reaction method using Y2 O3 and Eu2 O3 particles. In the solid state reaction methods, high temperature and long heating time are required for activation of rareearth components inside the matrix of the host materials.

a)

On leave from Korea Advanced Institute of Science and Technology. Address all correspondence to this author. e-mail: [email protected]

b)

J. Mater. Res., Vol. 14, No. 6, Jun 1999

http://journals.cambridge.org

Downloaded: 03 Mar 2015

Additionally, the prepared particles have irregular shape and tend to agglomerate. Liquid solution methods are also frequently applie