2002 Fiscal Year Final Research Report Summary
Efficient phosphors for mercury-free fluorescent lamps
| Project/Area Number |
12650817
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
工業物理化学
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| Research Institution | Tokyo University of Technology |
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Principal Investigator |
YAMAMOTO Hajime Tokyo University of Technology, School of Bionics, Professor, バイオニクス学部, 教授 (00247298)
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| Co-Investigator(Kenkyū-buntansha) |
OKAMOTO Shinji Nara Institute of Science and Technology, Graduate School of Materials science, Assciate researcher, 物質創生科学科, 助手 (50324976)
MITA Yo Tokyo University of Technology, Faculty of Engineering, Professor, 工学部, 教授 (20200040)
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| Project Period (FY) |
2000 – 2002
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| Keywords | Mercury-free lamp / Vacuum ultraviolet / Phosphor / Rare-earth ion / Quantum efficiency / Energy transfer / Non-linear luminescence |
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| Research Abstract |
[I]Efficient phosphors were surveyed to convert VUV light of 172nm wavelength obtained from Xe excimers to visible light. In 2001, we investigated feasibility of quantum cutting processes in stable oxides, specifically rare-earth orthophosphates. The results showed that nonradiatative relaxation from a high-energy excited level of a rare-earth ion and energy transfer between rare-earth ions in the UV region can reduce the probability of the quantum cutting. However, energy transfer from Pr3+ or Tm3+ to Gd3+ leads to efficient Gd3+ luminescence line at 312nm, which can be applied to lamps, which activate photoactive catalysis. This phenomena result from simple electronic configurations of Pr3+ or Tm3+, which have two 4f electrons or holes.
[II]In 2002, we investigated materials excited by energy transfer from a host to an activator ion.
(1)Substitution of Y by Gd in red-emitting YAIO3:Eu3+ gives rise to 30% increase in efficiency under 172nm light excitation. This remarkable effect result
… More
s from a red shift of the absorption edge of the host crystal by Gd substitution. We also developed a synthesis method to provide a single-phase material of high efficiency, which uses theta alumina as a starting material and firing temperature as high as 15000.
(2)In efficient red phosphor, SrTiO3:Pr3+, Al, energy is provided from the bound exciton to Pr3+.This work has shown that energy overlap between the fundamental absorption band of the host and 4f-5d absorption band of Pr3+ is correlated with the luminescence efficiency.
[III]Bright warm-white emission was discovered by cathode-ray excitation of rugged powder layers of insulater materials. This emission appears above the threshold electron-beam current and drastically increases in intensity with an increase in the beam-current density. The lowest threshold so far obtained is 0.02mA under 25kV electron excitation with a beam diameter of about 0.3mm. This emission may be a candidate of new non-mercury light source if the threshold can be further decreased. Less
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