Research On Novel Luminescent Materials For Field Emission Displays

Field emission display (FED) is increasingly becoming one of the significantly emerging candidates for the next generation of information display device. Its advantages include portable size with low power consumption, broad viewing angle, and wide operating-temperature range. Currently the reliability and the lifetime of monochrome and full color FED panels on a commercial basis are actively being characterized. Present phosphors used in FED prototypes include Y2O3:Eu, Y₂O₂S:Eu, SrGa₂S₄:Eu, ZnGa2O4:Mn, Y₃Al₅O₁₂:Tb, ZnO:Zn, and Y₂SiO₅:Ce, etc. However, all of these phosphors are not very satisfactory due to their poor efficiency and the degradation under the bombardment of high current density electron beams. Additionally the low conductivity also limits the usefulness of these oxide phosphors. It is important to develop novel phosphors with high luminescent efficiency, good stability and reasonable conductivity for promoting FED properties. The phase relationships of the systems such as R₂O₃-Ga₂O₃, MO-Ga₂O₃, R₂O₃-GeO₂ and R₂O₃-TiO₂(R=rare earth element, M=alkaline-earth metal) were investigated by solid-state reactions at high temperatures. The new phases including R₃GaO₆(R=Y, Eu, Tb, Dy, Ho, Er), R₄GeO₈ (R=Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu) and Sr₄Ga₂O₇ were synthesized, and their unit cell parameters were determined by the powder x-ray diffraction. The photoluminescent and cathodoluminescent properties of Eu³⁺, Tb³⁺, Bi³⁺activated these hosts from the above-mentioned systems were investigated. Good cathodoluminescent properties are found for these phosphors such as Gd3Ga5O12:Tb,Y3GaO6:Eu,Gd₃GaO₆:Bi. The adsorption spectra and the alternate current impedance spectra of these hosts were also measured. The relation among the energy gap, crystal structure, conductivity and luminescence of these hosts were investigated. The energy gap of the hosts depends on their crystal structures and the energy gap of the raw material oxides. The energy gap of the hosts is an important factor on the conductivity and the luminescence of their related phosphors. Some foundations and directions are provided for the researches of FED phosphors in this paper.