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A series of LuNbO4:xDy3+ (x = 0–0.20) phosphors was prepared using a high-temperature solid-state reaction technique. X-ray diffraction (XRD) along with Rietveld refinement, field emission scanning electron microscopy (FE-SEM) observations, diffuse reflectance spectra (DRS), UV-vis photoluminescence (PL), fluorescence decays, PL quantum yields (QYs), and low-voltage cathodoluminescence (CL) were employed to characterize the phosphors. Nonradiative relaxation and host sensitization dramatically influence the LuNbO4:Dy3+ luminescence spectra and decay dynamics. It is shown that cross-relaxation arising from electric dipole–dipole interactions between adjacent Dy3+ ions is the leading mechanism of quenching the Dy3+ emission. The host sensitization for Dy3+ emission in LuNbO4 was confirmed and the energy transfer efficiency from the host to Dy3+ increased with increasing Dy3+ doping concentration/temperature. Upon excitation with ultraviolet light (261 nm) and a low-voltage electron beam (2 kV, 127 μA cm−2), the synthesized LuNbO4:Dy3+ phosphors show both the blue broadband emission of the LuNbO4 host and the characteristic emission of Dy3+ (the dominant one is the 4F9/2→6H13/2 transition, yellow), and the luminescence colour of the LuNbO4:Dy3+ phosphors can be tuned over a large gamut of colours by varying the Dy3+ doping concentration, and a single-phase intense white-light-emission has been achieved in the LuNbO4:0.015Dy3+ phosphor. On the basis of the good UV-vis PL and CL properties, LuNbO4:Dy3+ phosphors might be promising for applications in UV light-emitting diodes (UV-LEDs) and field emission displays (FEDs). [ABSTRACT FROM AUTHOR]

Photoluminescence properties of Ba2MgSi2O7:Eu2+ synthesized by a solid-state reaction method are first investigated in the vacuum ultraviolet (VUV) to visible (vis) excitation energy range. The band gap of the host is found to be around 7.44 eV. The incorporation of Eu2+ leads to bright green luminescence with weak thermal quenching above room temperature. Cathodoluminescence (CL) properties under low-voltage excitations are then studied, and the results suggest a potential application of the compound in field emission displays (FEDs). Electronic properties of the compound are finally calculated by a hybrid density functional theory (DFT) method, and are discussed in association with observed luminescence properties. [ABSTRACT FROM AUTHOR]

Ultraviolet and vacuum ultraviolet spectra are reported for Ce3+ and Eu2+ singly doped into the Sr5(PO4)3Cl lattice, synthesized by a solid-state process. The maxima of the emission intensities are at 346 nm (Ce3+) and 442 nm (Eu2+), with lifetimes of 25 ns and 494 ns, respectively. The Ce3+ excitation spectra exhibit five bands assigned to vibronic structures of the 4f1→ 5d1 electronic transition, in addition to the host absorption at 166 nm at 295 K. The 5d centroid shift is similar to that in SrCl2:Ce3+. The Eu2+ excitation spectrum is mainly comprised of two 4f7→ 4f65d broad bands between 200 nm and 450 nm, peaking at 343 nm and 275 nm. Both of the singly doped systems exhibit concentration quenching, with energy transfer rates being in the low (μs)−1 range for concentrations up to 4 at.% of total cations. The energy transfer rates are linearly and quadratically related to dopant ion concentrations of Ce3+ and Eu2+, respectively. The energy transfer between Ce3+ and Eu2+ in the co-doped Sr5(PO4)3Cl lattice has been studied by the analysis of intensity and decay measurements of both Ce3+ and Eu2+ emissions. The electric dipole–electric dipole transfer has an efficiency of 91% in Sr4.8−xCe0.01EuxNa0.01(PO4)3Cl, with a critical distance of 21 Å. Although energy transfer between Ce3+ and Eu2+ upon excitation into the overlapping Ce3+/Eu2+ absorption band is definitely demonstrated by the dramatic shortening of Ce3+ lifetime, the emission of Eu2+ is also enhanced at low Ce3+ concentrations using exclusive excitation into the Eu2+ absorption band. The quantum yields (QY) of the co-doped system approach those of BaMgAl10O17:Eu2+ (BAM) for the excitation wavelengths of 317 and 365 nm, but are inferior for 254 nm excitation. The addition of 1 at.% Ce3+ to Sr4.98Eu0.02(PO4)3Cl increases the QY by ∼20% of the original value. The cathodoluminesce of the co-doped phosphor is comparable to that of BAM, with CIE coordinates of the emission (0.274, 0.237), so that the application as a field emission display phosphor is proposed. [ABSTRACT FROM AUTHOR]