Nanocrystalline Zn 1x Gd x O (x = 0, 0.02, 0.04, 0.06, and 0.08) ceramics were synthesized by ball milling and subsequent solid-state reaction. The transmission electron microscopy (TEM) micrograph of as synthesized samples revealed the formation of crystallites with an average diameter of 60 nm, and the selected area electron diffraction (SAED) pattern confirmed the formation of wurtzite structure. A red shift in the band gap was observed with increasing Gd 3+ concentration. The photoluminescence of nanocrystalline Gd 3+ doped ZnO exhibited a strong violet-blue emission. Concentration dependence of the emission intensity of Gd 3+ in ZnO was studied, and the critical concentration was found to be 4 mol% of Gd 3+ . The Gd 3+ doped ZnO exhibited paramagnetic behavior at room temperature, and the magnetic moment increased with Gd 3+ concentration.

Molybdenophosphates Na 2 Y 1-x Eu x (MoO 4 )(PO 4 ) and Na 2 Y 1-x Tb x (MoO 4 )(PO 4 ), were shown to exhibit photoluminescence (PL) properties for a broad substitution range. Under near-UV excitation, Na 2 Y(MoO 4 )(PO 4 ):Eu 3+ and Na 2 Y(MoO 4 )(PO 4 ):Tb 3+ phosphors show emission lines corresponding to 5 D 0 → 7 F J (J = 0-4, red) and 5 D 4 → 7 F J (J = 4-6, green), respectively. The critical concentrations of Eu 3+ and Tb 3+ are 0.5 and 0.7, respectively beyond which concentration quenching occurs. This behavior is explained on the basis of Eu 3+ -Eu 3+ and Tb 3+ -Tb 3+ distances. For x = 1, Na 2 Tb(MoO 4 )(PO 4 ), emission from the 5 D 4 level of Tb 3+ that appears yellow in color is observed.

Eu 3+ -doped LiInO 2 phosphors have been synthesized by solid-state reaction at 1000°C and characterized by powder X-ray diffraction and photoluminescence studies. These phosphors show emission lines of Eu 3+ corresponding to 5 D 0 -7 F J ͑J = 1,2͒ transitions under 466 nm excitation. Among these emission transitions, the 5 D 0 -7 F 2 electric dipole transition at 614 nm is the predominant one. The critical concentration of Eu 3+ is x = 0.05 in LiIn 1−x Eu x O 2 , beyond which concentration quenching is observed. The emission intensity of LiIn 0.95 Eu 0.05 O 2 phosphor is ϳ1.3 times that of Y 2 O 2 S:Eu 3+ ͑Nichia͒.A large number of Eu 3+ activated phosphors have drawn considerable attention in view of their application as red phosphors in color television tubes and field emission displays. For these applications, phosphors exhibiting pure red emission with a high efficiency are required. Knowledge of the factors influencing the efficiency of phosphors is limited. For example, the phosphors Gd 2 O 3 :Eu 3+ and YVO 4 :Eu 3+ are highly efficient 1,2 and the phosphors Gd 2 Ti 2 O 7 :Eu 3+ and Y 2 MoO 6 :Eu 3+ are less efficient. Eu 3+ red emission depends on strong distortions in the host lattice. The intensity of the 5 D 0 -7 F 2 ͑red emission͒ transition varies when the polarization of the surrounding anion changes by crystal chemical substitutions in the host lattice; this has been observed in various garnets. 3 The difference in energy between the ground and excited states in Eu 3+ is typically ϳ3.2 eV; therefore, large bandgap oxides are required as hosts for incorporation of Eu 3+ and to obtain reasonable emission intensities.Phosphors with a low bandgap host are needed for application in field emission displays ͑FEDs͒ to minimize charging effects. Y 2 O 2 S:Eu 3+ red phosphor is presently used in FEDs; it can be considered as a wide bandgap semiconductor ͑E g = 4.6-4.8 eV͒. 4,5 Blasse and Bril have studied a series of Eu 3+ containing mixed metal oxides with rock salt-type structure and observed that, when excited with 250-270 nm wavelength radiation, both LiIn 0.95 Eu 0.05 O 2 and NaIn 0.95 Eu 0.05 O 2 have a low quantum efficiency. 6 Recently, the phosphors SrIn 2 O 4 ͑E g = 3.6 eV͒: Pr 3+ , Tb 3+ , and CaIn 2 O 4 ͑E g = 3.9 eV͒: Pr 3+ , Tb 3+ have been studied as possible candidates for application in FEDs. 7,8 The electric dipole transition of Eu 3+ is the ideal choice for red emission; the challenge is to find host lattices with a low bandgap which can give rise to reasonable intensities for the Eu 3+ emission. Thus, it is of interest to search for materials with an optimum bandgap ͑the lowest possible͒ which can give rise to a reasonable emission intensity of Eu 3+ . In our endeavor to explore phosphor materials satisfying the above criteria, we have synthesized and studied a series of Eu 3+ -doped LiInO 2 compounds and shown that LiIn 0.95 Eu 0.05 O 2 is a promising phosphor. ExperimentalLiIn 1−x Eu x O 2 ͑x = 0.01-0.07, in steps of 0.02 and x = 0.1͒ and NaIn 0.95 Eu 0.05 O 2 and NaLa 0.95 Eu 0.05 O 2 ...

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