Green-emitting Ba1.468Sr0.5SiO4 : Eu0.012, Y0.02 phosphor powders under long-wavelength ultraviolet light were prepared via high-temperature flame spray pyrolysis from spray solutions with and without NH4Cl flux. The effects of the temperature of the diffusion flame and the NH4Cl flux on the morphologies, crystal structures and photoluminescence intensities of the Ba1.468Sr0.5SiO4 : Eu0.012, Y0.02 phosphor powders were investigated. The phosphor powders obtained from the spray solution with the NH4Cl flux had higher photoluminescence intensities compared to phosphor powders obtained from the spray solution without the flux. The photoluminescence intensity of the phosphor powders obtained from the spray solution without the flux decreased as the flow rate of the fuel gas increased. On the other hand, the photoluminescence intensity of the phosphor powders obtained from the spray solution with the flux increased as the flow rate of the fuel gas increased. The difference of in the phase purity and morphology of the powders affected the photoluminescence intensities of the phosphor powders.

The phase transformations and luminescent properties of Eu-doped Ca1-xSrxAl2O4 phosphors were investigated. Ca1-xSrxAl2O4:Eu2+ phosphors were synthesized by a solid-state reaction with a flux, H3BO3. A phase transformation from monoclinic CaAl2O4 to monoclinic SrAl2O4 was observed as the x values increased. A high-temperature hexagonal phase of SrAl2O4 was formed during this transformation as an intermediate phase under an H2 atmosphere due to oxygen vacancies; this did not occur in an air atmosphere. Accordingly, the emission spectra shifted from a blue region to a green region as x increased.

Both photoluminescence and thermal characteristics for SrAl2O4:Eu+2,Dy+3 phosphors synthesizedwith various aluminum compounds (α-Al2O3, γ-Al2O3, amorphous-Al2O3 and Al(OH)3) were investigated in thisstudy. The formation temperature of the host SrAl2O4 crystal is changed by these various aluminumcompounds, as a result of the different thermal decomposition temperature of SrCO3 phase. Among thesecompounds, the amorphous-Al2O3 phase shows the lowest formation temperature of the host SrAl2O4 crystal.The PL emission and excitation spectra of SrAl2O4:Eu+2, Dy+3 phosphor are not affected by these aluminumcompounds. After the removal of the Xenon lamp excitation (360nm), however, the excellent long-phosphorescent property of the phosphor is obtained by the amorphous-Al2O3 phase, although the decay timefor all phosphors decrease exponentially.

Eu3+ doped YGdO3 phosphors particles which have fine size and narrow size distribution with non aggregated uniform morphology were prepared by solvent evaporation method for the improvement of emission efficiency. Several parameters have been investigated in this study such as the influences of composition ratio of host materials, calcination temperature, amount of activator, surfactant, pH and flux on the photoluminescence intensity, particle size and dispersion. Eu3+ doped YGdO3 phosphor presented a strong narrow band emission peak at 612nm. The maximum emission intensity ofYGdO3:Eu3+ occurred when Eu3+ concentration is 3wt% under vacuum ultra violet excitation. Prepared phosphors were found to have small round-shaped particles about 150nm in size. The addition of PVA as a surfactant inhibits the grain growth and the agglomeration of particles efficiently by reducing the oxygen bridge bonds. As the pH reduces, PL intensity increase due to reducing the formation of oxygen bridge bonds. The particles prepared from solvent evaporation method with 5wt% LiCl were found to have 120% PL intensity compare to particles prepared without LiCl flux.

Field emission display(FED) is actively investigated in view of the development of full color flat-panel display, which can replace some cathode-ray tube(CRT). Thus, the development of new phosphors appropriate for FED is urgently needed and has been actively investigated. In this work, SrTiO3:Pr3+ phosphor was prepared by sol-gel method and the coating was applied by sol-gel method combined with sonication on these phosphor's surface into diluted precursor solution. It was found that very fine particles of coating material were formed on phosphor's surface. The luminescent intensity of SrTiO3:Pr3+ phosphor coated with SiO2 and Al2O3 was considerably increased without any noticeable change in color chromaticity. The optimum concentration of coating material was found to be 1wt% and the optimum pH value of the solution was 10.

Y2-xGdxO3:Eu, phosphors for plasma display panel(PDP), were prepared by Pechini method which use yttriun chloride, gadolinium chloride, and europium oxide as starting materials. This method is a different way to the synthesis of europium(Eu)-doped phosphors, and it consists of the formation of a polymeric resin obtained by polyesterification between metal chelate compounds and a polyfunctional alcohol. This needs lower temperature than solid-state synthetic method. The prepared Y2-xGdxO3:Eu phosphor particles had spherical shape and coherence. The luminescence intensity of Y2-xGdxO3:Eu phosphor particles increased according to the increase of gadolinium(Gd) content(to 0.8mol%), and Y1.2Gd0.8O3:Eu phosphors had the highest luminescence intensity under vacuum ultra violet(VUV) excitation. The optimum concentration of Eu in the phosphor and optimum calcination temperature was 3wt% and 1100℃. The prepared phosphors were consist of particle, and its size was between 100nm and 150nm. Among the different polyfunctional alcohols, diethylene glycol(DEG) improved the luminescence intensities of phosphors more than other additives. The Pechini method proved that it is demonstrated to be suitable for the synthesis of phosphors used in PDP.

In this study, the ZnS composite powders for host material in phosphor was synthesized in situ by mechanical alloying. As the mechanical alloying time increases, particle size of ZnS decreases. ZnS powders of in a mean size was fabricated by mechanical alloying for 10h. The crystal structures of ZnS powders were investigated by X-ray diffraction and the photo-luminescence properties was evaluated with the optical spectra analyzer. The steady state condition of mechanically alloyed ZnS was obtained as a mean particle size of in 5h milling. The sphalerite and wurtize structures coexist in the ZnS mechanically alloyed for 5h. The ZnS powder mechanically alloyed for 10h grows to the sphalerite structure. And the strong emission peaks of ZnS are observed at 480 nm wave length at the powders of mechanically alloyed for 10h, but the sphalerite and wurtize structures in ZnS coexist and emission peaks are not appeared at the powders of mechanically alloyed for 10h.