用ceyag陶瓷材料制備高功率白光led及其光學(xué)性能研究畢業(yè)論文外文翻譯

1、中文 1664 字英文原文Preparation and Optical Properties of Transparent Ce:YAG Ceramics for High Power White LEDS. Nishiura1, S. Tanabe 1, K. Fujioka2, Y. Fujimoto2 and M. Nakatsuka21 Graduate School of Human and Environmental S

2、tudies, Kyoto University,Yoshida nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan2 Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka,Suita, Osaka 565-0871, JapanE-mail: s.nishiura@nctdd.mbox.media.kyoto-u.a

3、c.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

4、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 increa

5、sing 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 valu

6、e of luminous efficacy of the white LED was 73.5 lm/W.1. IntroductionWhite LEDs are now extensively spotlighted as general illumination as well as backlight of the liquid crystal display (LCD), car headlights and indica

7、tor 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 Garn

8、et) (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 du

9、e 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 org

10、anic 72 h. The resulting precipitate was centrifuged and washed seven times with distilled water and ethanol. Thenit was oven-dried at 80 ºC for 12 h and at 200 ºC for 72 h. The precursor powders obtained wer

11、e heated at 800 ºC for 100 h in air to remove the organicsubstances. The powders were heated at 1200 ºC for 90 min in air to get the YAG powder.The milling process was carried out to grind a wide variety of t

12、he powder size into 200 ~ 300 nm averages. In this process, ethanol, a dispersant (Kyoeisha Chemical Co., LTD, Flowlen G-700) and SiO2 were added to the powder at the weight ratio for powder:ethanol of (1:5), 0.4 wt% of

13、 the ethanol and 0.2 wt% of the powder, respectively. After the milling process, a binder (Sekisui Chemical Co., LTD, S-LEC BL-1) was added in the slurry at 0.5 wt% of the powder and the slurry was milled with nylon bal

14、ls for 24 h. Then, the slurry was poured into a mold located on a gypsum plate. It was dried at room temperature for 72 h. The caked slurry was heated to remove the organic substances at 800 ºC for 00 h under O2 at

15、mosphere. Finally, it was heated at 1780 ºC for 20 h under vacuum. The YAG ceramics obtained were cut and polished carefully. The thickness was set in the range of 0.1 ~ 0.8 mm.2.2. Measurement The microstructure o

16、f the YAG ceramics was observed by a confocal scanning laser microscopy (Olympus Corp., OLS1200). The optical transmittance of the mirror-polished samples on both surfaces was measured over the wavelength region from 20

17、0 to 850 nm using a spectrophotometer (Shimadzu Corp., UV-3600). The photoluminescence (PL) of the Ce:YAG ceramics was measured under 465 nm LED (Nichia Corp., NFSB036B). In the optical measurement, the Ce:YAG ceramics w

18、ere mounted on the LED. The spectral power and photon distribution of total radiant flux of PL spectra were measured by using an integrating sphere (Labsphere, Inc., LMS- 100) which was connected to a CCD detector (Ocea

19、n Optics, Inc., USB2000) with an optical fiber. A standard halogen lamp (Labsphere, Inc., CLS-600) was used for calibrating this measurement system. The luminous efficacy (lm/W) of the Ce:YAG ceramics was calculated fro