Su-Hua Yang

Electrophoretic Prepared ZnGa2 O 4 Phosphor Film for FED

In this study, the low voltage ZnGa 2 O 4 phosphor film for field emission display (FED) is prepared by electrophoresis. The influence of the deposition parameters, such as deposition time, deposition voltage, electrode distance, and stirring speed on the electrophoresis and luminescence of phosphor film are investigated. The optimal deposition parameters for electrode distance. stirring speed, electrode bias, and deposition time are 20 mm, 450 rpm, 50 V, and 40 s, respectively. The optimum phosphor film thickness is 8-10 μm. For improving the crystallization and luminescence of the as-deposited phosphor film, it is annealed in various atmospheres. A luminance of 2080 cd/m 2 is obtained when phosphor film is annealed in 25%O 2 /Ar atmosphere and measured at an electron-gun voltage of 5 kV and an anode current of 30 A. The luminance efficiency of phosphor films prepared by electrophoresis is about 15 times higher than that prepared by the sedimentation method.

Influence of Doping and Coating on the Photoluminescence Properties of Yttrium Aluminum Garnet Phosphors

This paper presents the influence of doping and coating on the photoluminescence (PL) properties of yttrium aluminum garnet (YAG) phosphors. Transition-metal Mn and rare-earth (Re) element doped YAG phosphors were synthesized by the solid-state sintering method. Mn and Re elements such as Eu and Ce were used as activators; they were doped and co-doped into YAG. The maximum PL intensity was obtained from YAG:Ce phosphor. X-ray photoelectron spectrometry analyses investigated the chemical bonding states of Zn 2p, In 3d, and O Is of the conductive-coated YAG:Ce phosphor. The PL intensity of YAG:Ce was enhanced via ZnO and In 2 O 3 coating and surface state modification.

Novel SrGa2 O 4 Phosphor for Tunable Blue-White Luminescence

A tunable blue to blue-white SrGa 2 O 4 phosphor was prepared with a solid-state reaction method by varying the composition concentration of source materials. The decomposition temperature and weight loss of Ga 2 O 3 and SrCO 3 were evaluated by thermogravimetric analysis. The deficiency of Ga in SrGa 2 O 4 phosphor can be compensated by increasing the molar ratio of Ga 2 O 3 /SrCO 3 . Photoluminescence measurements show that Ga is the luminescence center of strontium gallate phosphor. When the molar ratio of Ga 2 O 3 /SrCO 3 is 1, the emission wavelength of SrGa 2 O 4 phosphor is ∼402 nm, which is referred to the 4 T 1 → 4 A 2 transition of electrons in Ga d orbits. Crystallization of SrGa 4 O 7 was observed as the phosphor was prepared at a higher molar ratio of Ga 2 O 3 /SrCO 3 . The ligand field and the electron transferring mechanism in Ga will be modulated by the development of SrGa 4 O 7 . Thus, the emission wavelength of phosphor is altered from 402 to 430 nm where the electron is transferred from 4 T 2 A exciting state to 4 A 2 ground state while the emission spectrum is broadened.

Cathodoluminescence of a White ZnGa2O4 ∕ ZnO Phosphor Screen

The optimal white luminescence of ZnGa2O/ZnO screen is obtained when it is annealed at 400℃, in this condition, the resistivity of the screen is low, so the electrons in Ga will have a higher probability to transfer from 2E(subscript B) to 4A2 energy levels.

Luminescence Enhancement Mechanism of ZnGa2O4 Phosphor Screen with an In2O3 Buffer Layer

The luminescence enhancement mechanism of a white ZnGa 2 O 4 phosphor screen with an In 2 O 3 buffer layer was studied by growing ZnGa 2 O 4 with optimal sputtering parameters and varying the deposition conditions of In 2 O 3 . A ZnGa 2 O 4 film with better crystallization and smaller grains was obtained when it was deposited on In 2 O 3 . These qualities revealed that the resistivity of the phosphor screen was correlated with the surface roughness and resistivity of the In 2 O 3 buffer layer. The photoluminescence spectra of the phosphor screen revealed that the ligand field of the Ga luminescence center was not modified when the In 2 O 3 deposition parameters were varied; however, the emission intensities were altered due to the electron-transition probability in the Ga energy levels changing with the crystallization of phosphor. A significantly enhanced emission from the phosphor screen was observed by improving the crystallization, surface morphology, and resistivity of the prepared ZnGa 2 O 4 phosphor film with the In 2 O 3 buffer layer.

Effect of Substrate Properties on Luminescence of White ZnGa2O4 Phosphor

The variations in the crystallization and luminescence characteristics of ZnGa2O4 phosphor screens deposited on various substrates were investigated. The ZnGa2O4 phosphor deposited on Corning glass, indium tin oxide glass and Si substrates was polycrystalline. However, when a ZnO buffer layer was prepared, it was amorphous; it was polycrystalline after annealing at a temperature higher than 300 °C. The optimal cathodoluminescence was caused by the low backscattering of electrons, a large emission area, and the specific crystallization of the ZnGa2O4 phosphor grown on the ITO glass substrate. When a ZnO buffer layer was prepared, small ZnGa2O4 grains were grown; consequently, the emission area and CL intensity increased. Resistivity measurement revealed that the conductivity and cathodoluminescence are improved by thermal annealing.