On the basis of the possibility that there might exist a mixed composition of the Y(As,Nb,P,V)O4 system of better luminescent performance than the single-compound phosphors at the VUV excitation, a solution combinatorial chemistry synthesis and characterization was employed in the present investigation. Quaternary and ternary combinatorial libraries were designed to implement an efficient screening process. In parallel, the first-principle calculations were also carried out on the basis of the density functional theory to give a reasonable interpretation to the results from the combinatorial chemistry screening process. It was found that a new phosphor, Y0.9(P0.92V0.03Nb0.05)O4:Eu3+, which was obtained through the three-step combinatorial screening, shows promising luminance and CIE color chromaticity that could be comparable to the commercially available red phosphor used for the PDP application. As a result of the luminescent mechanism study in association with the calculated density of states (DOS), the entire energy transfer route under the 147-nm excitation was revealed for the newly found phosphor, Y0.9(P0.92V0.03Nb0.05)O4:Eu3+.

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Field emission displays (FEDs) are currently being explored as potential flat panel displays. Low power display markets are highly competitive, therefore low-voltage cathodoluminescent (CL) phosphors have become an important area of phosphor research. For the application of full color FEDs, efficient new phosphor materials with good chromaticity and high brightness must be developed. We have focused our attention on the Y 2 O 3 -Nb 2 O 5 system regarding requirements of new materials for low-voltage blue phosphors.According to the Y 2 O 3 -Nb 2 O 5 phase diagram, a compound with the composition YNbO 4 (ϭY 2 O 3 иNb 2 O 5 ) and a berthollide phase based on Y 3 NbO 7 (ϭ3Y 2 O 3 иNb 2 O 5 ) were found in this system. 1,2 Contrary to the cubic phase of Y 3 NbO 7 with a fluorite-related structure, the compound YNbO 4 has two polymorphs, 3-6 low-temperature monoclinic (M-phase, fergusonite structure) and high-temperature tetragonal (T-phase, scheelite structure) forms. The monoclinic form of YNbO 4 transforms into a tetragonal structure at 900ЊC. 1 Yttrium niobate is optically active and exhibits a strong and broad blue emission band, attributed to a charge transfer transition of the tetrahedral [NbO 4 ] 3Ϫ molecular ion. There have been some investigations either on Bi activated yttrium niobate by Blasse and Bril 7-9 or on rare earth niobate compounds, in particular the GdNbO 4 :Bi phosphor by Grisafe and Fritsch. 10 However, such efforts did not meet the requirement for actual display applications. Later Ropp 11 reported systematic studies of niobates doped with rare earth ions and indicated that yttrium niobates activated by rare earth ions always showed lower efficiency than the host material as a self-activated phosphor. Recent studies by Vecht et al. [12][13][14]16 showed that the bismuth activated yttrium niobate could be used as a low-voltage saturated blue phosphor for FEDs.We therefore studied the synthesis of blue emitting phosphors in the Y 2 O 3 -Nb 2 O 5 system and examined the relationship of photo-and cathodoluminescent properties with their structures. In this study, yttrium niobate phosphors doped with Bi were prepared by the solidstate reaction technique. The optimization of synthetic processes and the effect of Y/Nb ratio on the luminescent properties were investigated, specifically.Even though YNbO 4 and YNbO 4 :Bi are well-known phosphors, there have been no theoretical approaches to interpret their luminescence. Thus we have initiated calculations on the electronic structure of YNbO 4 using the density functional method. The excitation and emission spectra of YNbO 4 and YNbO 4 :Bi phosphors are interpreted with the calculated results regarding the charge transfer gap of YNbO 4 and the effect of bismuth in YNbO 4 :Bi phosphor.Experimental Preparation of phosphor.-Bismuth doped YNbO 4 phosphors were made from the starting materials Y 2 O 3 , Nb 2 O 5 , and Bi 2 O 3 (all supplied by the High Purity Chemical Laboratory Co. Ltd., at 99.99% purity) powders. Required amounts of the corresponding powders...