Fabrication And Performance Optimization Of The Novel Oxide Scintillation Ceramics

Scintillators are one of the phosphors which can convert X and y-rays or other high-energy particles into the visible-ultraviolet (UV) photons. In order to satisfy the ever-growing need of modern medical imaging (CT), security detection, high energy physics and homeland security applications, it puts forward rigorous demands for scintillation materials: higher light yield,faster decay time, superior radiation hardness and low cost etc.. Eu3+ doped sesquioxide scintillation materials have attracted much attention because of its high light yield. In the 1980s,(Y,Gd)2O3:Eu ceramic scintillations has been developed and used in X-CT successfully by General Electric. Compared to Y2O3, Lu2O3 possesses higher density and larger effective atomic number, which results in better X-ray stopping power. At the same time, it is found that co-doping of Gd in Y2O3:Eu and Lu2O3:Eu can enhance X-ray fluorescence efficiency. In this dissertation, we focused on the fabrication and performance optimization of the (Y,Gd)2O3:Eu and (Lu,Gd)2O3:Eu ceramics based on Y2O3:Eu ceramics.First, influence of the annealing temperatures on the optical and luminescence performances of Y2O3:Eu scintillation ceramics has been investigated. The luminescence efficiency was elevated after annealing. However, the optical quality of the ceramics in shortwave range was decreased, mainly due to the inflation of residual pores, which results in the scattering of incident light. Co-doping of the Gd3+ ions in Y2O3:Eu ceramics was also studied. It is found that the energy transfer between the Gd3+ and Eu3+ can increase the luminescence efficiency, as well as the stopping power for ionizing radiation detection due to the higher density. What's more, the co-doping of the Gd3+ ions decreased the decay time of 5D0?7F0 transfer of Eu3+ ions. From the signal of thermoluminescence of Y2O3:Eu and(Y,Gd)2O3:Eu ceramics, which can be seen that the deep-level traps became shallow and its concentration reduced with Gd3+ ions doped in Y2O3:Eu ceramics.The co-doped (Lu,Gd)2O3:Eu scintillation ceramics with stoichiometry of (Lu1-xGdx)2O3:Eu (x=0, 0.1, 0.3, 0.5, 0.7, 0.9) were also fabricated without sintering aids. Solid solution of Lu2O3 and Gd2O3 can be achieved when the concentration of Gd3+ was less than 50%. The energy gaps of the (Lu,Gd)2O3:Eu ceramics decreased with the increase of Gd3+concentration, which would result in the elevation of light yield in theory. Also, it is found that the intensity of PL and X-ray fluorescence were enhanced with Gd3+ ions increased. When the doping concentration of Gd3+ was above 70%,the crystal structure of the (Lu,Gd)2O3:Eu ceramics transferred from cubic structure to monoclinic or hexagonal structures. The emission of the monoclinic (Lu,Gd)2O3:Eu ceramics was similar to that of the monoclinic Gd2O3, while the intensity was much weaker.At last, the irradiation damage resistance of the Y2O3:Eu and(Lu,Gd)2O3:Eu scintillation ceramics were also studied. For both materials, new absorption bands appeared in the range of 300-700nm after irradiation under X ray, which may account from the Eu3+/e- complexus defect or impurities (such as Yb3+) of the raw materials. Compared with the Lu2O3:Eu ceramics, the luminescence of the (Lu,Gd)2O3:Eu ceramics decreased much more slowly with the prolonging of the irradiation time, which means the Gd3+ doping in benefit to the irradiation damage resistance.