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Eu3+ doped Lu2O3 phosphor typically has an emission wavelength in red region. The transition of Eu3+ is due to the 5D0 → 7F2 transition at 610 nm. The typical red emission wavelength that is suitable for CCDs. So the phosphor is useful for X-ray imaging application using CCD. The Host material, Lu2O3 has high density (~9.42 g/cm3) and high effective Z-number (Zeff = 63) in comparison with commercial phosphors. For that reasons, the absorption efficiency of the high energy photons (X-rays or gamma rays) is excellent with the other one. The efficiency of radiation detection of europium doped lutetium oxide Lu2O3:Eu3+ is very high, approximately 80% of the CsI:Tl. And it has large enough band gap between valance and conduction bands. So it can accommodate various luminescence activators such as Eu, Tb or Tm etc.
To produce the Lu2O3:Eu3+ phosphors, I used a co-precipitation method using the lutetium nitrate hydrate [Lu(NO3)3·6H2O], europium nitrate hydrate [Eu(NO3)3·6H2O] and diethanolamine [C4H11NO2]. The phosphors were sintered from 1,100°C to 1,700°C by horizontal electric furnace in air atmosphere and then,I obtained the luminescence properties of the phosphor such as emission and excitation spectra, decay time, relative light yield and the radiation hardness etc. I also examined the crystal structure of the phosphor using FE-SEM and XRD. Lu2O3:Eu3+ has shown the highest efficiency sintered at 1,600°C for 4 hours and 6 % Eu3+ concentration. For the radiation hardness test, 45 MeV, 10 nA flux Proton beam (MC-50 cyclotron at the KIRAMS) was used. The total irradiation dose was approximately 105 ~ 106 Gy. I did not observe any remarkable change on the intensity of light emission and the range of emission wavelength. Hence I concluded that it is radiation hard and it can be applied high radiation fields as a medical image detector.
Thesis Advisor: Prof. Hongjoo Kim