Studies On The Luminescence Properties Of Vacuum Ultraviolet Phosphors Doped With Pr³⁺ Or Nd³⁺

The vacuum-ultraviolet (VUV) phosphors doped with rare earths was a kind of promising materials which could be used in mercury-free fluorescent lamps, high-efficient plasma display panels, and fast scintillator. With the development of VUV experimental methods including synchrotron station and the requirements for high-efficient VUV phosphors, a lot of VUV phosphors were studied to get more applicable VUV phosphors and to expand the understand for the high-energy levels of Lanthanides. So the research about the VUV phosphors was not only the need for application, but also the tendency of the development of the lanthanide energy levels theory.This thesis could be divided into several parts:1. Firstly, the thesis verified the application of original and modified Judd-Ofelt theory to ¹S₀ state of Pr³⁺. The results showed that it was possible to get more feasible calculating results using modified Judd-Ofelt theory. Therefore, it was necessary to modify the original Judd-Ofelt theory which would be applied to Pr^{3+ 1}S₀.2. Secondly, influence of defect on the luminescence of Pr³⁺ in aluminates and the thermal excitation from ¹S₀ state of Pr³⁺ in borates were also studied. As the results identified, at 20K the defect emission in host would be increased and above 100K the thermal excitation of ¹S₀ could be strengthened, and it was also concluded that both defects in hosts and thermal excitation from high-energy levels could decrease the quantum efficiency of Pr^{3+ 1}S₀, so these processes should be avoided for high-efficient quantum cutting materials.3. Thirdly, the VUV luminescent and decay properties of Pr³⁺ or Nd³⁺ doped in LiLuF₄ were also reported. From excitation spectra and decay curves, it could be concluded that there were energy transfer processes from Lu³⁺ to Pr³⁺ or Nd³⁺. Under excitation (65nm or 90nm) above the bandgap the decay curves of Pr³⁺ or Nd³⁺ were second-order exponential figures which were induced by the energy transfer processes from activators to defects. The lifetimes were less than 17.5ns. So from the response times the Pr³⁺ or Nd³⁺ activated LiLuF₄ was a kind of promising scintillator materials.4. The spectral and decay properties of powder and single crystal YPO₄:Nd³⁺ at different temperatures, different excitation or emission wavelength, and concentrations were also studied. The results showed that under excitation over the bandgap single crystal sample exhibited stronger defect luminescence, on the contrast the powder sample would show stronger defect emission under the excitation below the bandgap. At 200K, both powder and single crystal samples had the slower build-up times for Nd³⁺ 4f^n-15d emission, and the lifetimes were less than 9ns. Accordingly, from the aspect of response times YPO₄:Nd³⁺ was also a kind of better scintillator materials.