August 2001 Ž . Materials Letters 50 2001 92–96 www.elsevier.comrlocatermatlet Synthesis of LaPO :Ce,Tb phosphor particles by spray pyrolysis 4 I. Wuled Lenggoro a , Bin Xia a , Hiroaki Mizushima a , Kikuo Okuyama a, ) , Naoto Kijima b a Department of Chemical Engineering, Faculty of Engineering, Hiroshima UniÕersity, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527 Japan b Mitsubishi Chemical Corporation, Yokohama Research Center, Yokohama 227-8502 Japan Received 2 November 2000; accepted 13 November 2000 Abstract Spray pyrolysis method was applied to prepare submicron LaPO :Ce,Tb phosphor particles. The product characteristics 4 such as photoluminescence, crystallinity, and particle morphology were investigated under various preparation conditions and compared with those of commercial ones. The prepared powders showed 543-nm green emission characteristics. The maximum photoluminescence intensity was obtained at 15508C. q 2001 Elsevier Science B.V. All rights reserved. PACS: 78.55 ym; 81.20.Rg Keywords: Lanthanum phosphate; Cerium; Terbium; Phosphor; Luminescence; Powder; Spherical 1. Introduction Rare-earth doped multicomponent oxide particles have been widely studied for application of display devices, lights and detectors. LaPO :Ce,Tb phos- 4 phors have been used for the green component of three band emission type fluorescent lamp. It is important to develop a process that can produce particles having controlled characteristics such as morphology, composition and size for good lumines- cent characteristics. Phosphor materials are usually prepared via solid wx state 1 . The solid state route uses flux and requires Ž high reaction temperatures typically more than . 15008C , long heating times, and a milling process to ) Corresponding author. Tel.: q 81-824-247850; fax: q 81-824- 247850. Ž . E-mail address: okuyama@hiroshima-u.ac.jp K. Okuyama . obtain the pure phase and small particles. Therefore, particles produced by this route are agglomerated particles of irregular shape. In addition, the milling process reduces the brightness due to the destruction of surface structure of the phosphor materials. There have been some reports, which concern the mecha- nisms of luminescence of rare earth doped LaPO 4 w x 2–6 and the conventional or alternative methods on w x the preparation 7–15 . wx Hashimoto et al. 7 prepared LaPO :Ce,Tb parti- 4 wx cles by solid state method. Arul Dhas and Patil 9 synthesized LaPO by flash combustion of aqueous 4 w x solutions. Fujishiro et al. 10 prepared LaPO parti- 4 cles of 20-nm size by hydrothermal reaction, with w x refiringrpost annealing process. Heike et al. 14 prepared LaPO :Ce,Tb, LaPO :Ce, LaPO :Eu parti- 4 4 4 cles, ranging in size from about 10 to 50 nm, and fibers with width of 5–20 nm by wet chemical synthesis with changing pH of solution. These previ- 00167-577Xr01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S0167-577X 00 00422-5