用CeYAG陶瓷材料制备高功率白光LED及其光学能研究毕业论文外文翻译.docVIP

英文原文 Preparation and Optical Properties of Transparent Ce:YAG Ceramics for High Power White LED S. Nishiura1, S. Tanabe 1, K. Fujioka2, Y. Fujimoto2 and M. Nakatsuka2 1 Graduate School of Human and Environmental Studies, Kyoto University,Yoshida nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan 2 Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka,Suita, Osaka 565-0871, Japan E-mail: s.nishiura@nctdd.mbox.media.kyoto-u.ac.jp Abstract. Transparent Ce:YAG ceramics were synthesized from the Ce:YAG powder which was produced by co-preparation method of the hydroxides. The Ce:YAG ceramics exhibit a broad emission band peaked at 530 nm due to the 5d→4f transition of Ce3+. The transmittances of the samples obtained were 70 ~ 87 % at 800 nm. The absorption coefficient and emission intensity of Ce3+ were increased with the increase of the thickness. With increasing thickness of the sample, the color coordinates of the Ce:YAG ceramics under 465 nm LED excitation shifted from the blue region to the yellow region with passing nearby the theoretical white point. The highest value of luminous efficacy of the white LED was 73.5 lm/W. 1. Introduction White LEDs are now extensively spotlighted as general illumination as well as backlight of the liquid crystal display (LCD), car headlights and indicator light. The advantages of the LEDs are low electric consumption, high brightness and long lifetime [1]. The most common method to make the white LEDs is combining of a blue LED and Ce:Y3Al5O12 (Yttrium Aluminum Garnet) (Ce:YAG) phosphor packed with organic resins [2]. The function of the Ce:YAG phosphor is to absorb the blue light emitted from the blue LED and converts it to yellow light. The phosphor has a broad band emission due to the 5d→4f transition of Ce3+. The combination of two lights of the transmitted blue light and the fluorescent yellow light makes white light. However, this white LED has a disadvantage of thermal degradation of organic resins, which is cause