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Yb 2+ -doped NaBaPO 4 phosphors were synthesized by the conventional high-temperature solid-state reaction. The x-ray powder diffraction, photoluminescence excitation and emission spectra, and the decay curves, were measured. The crystallographic site-occupations of Yb 2+ ions in NaBaPO 4 host were assigned on the base of the luminescence spectra and the crystal structure. The luminescence natures of NaBaPO 4 :,Yb 2+ , e.g., the Stokes shift, the luminescence quenching temperature, and the activation energy of thermal quenching were reported. The thermal stability of luminescence was investigated on the base of the temperature-dependent emission intensities and the decay curves. Some anomalous luminescence properties, e.g., the larger Stokes shift, the short decay lifetimes, the lower quenching temperature and low activation energies for thermal quenching, were discussed. The luminescence was ascribed to impurity trapped exciton emission.

This paper reports on the preparation and detailed discussion of photoluminescence (PL) and energy transfer in new Ba 1.6 Ca 0.4 P 2 O 7 :Eu 2+ phosphors. The PL excitation and emission spectra reveal that the doped Eu 2+ ions occupy two different crystallographic sites. The concentration dependence of PL emission spectra indicates that energy transfer between two different Eu 2+ ions takes place. Decay kinetics of donor [Eu(1)] and acceptor [Eu(2)] ions luminescence have been analyzed. The possible energy transfer mechanism and the temperature dependence of the Eu 2+ luminescence decay kinetics have also been investigated in detail.

Luminescence properties of BaY 2 O 4 :Eu 3+ are investigated by the site-selective laser-excitation spectroscopy in the temperature region 15―300 K. The phosphors were synthesized by the Pechini-type sol-gel method for different Eu 3+ -concentrations. Three different crystallographic sites corresponding to two Y 3+ sites (Y1 and Y2) and the Ba site for Eu 3+ are identified from the excitation spectra due to the 7 F 0 → 5 D 0 transition. Crystal-field splittings of the 7 F 1 and 7 F 2 multiplets lead to classify three different sites for Eu 3+ in BaY 2 O 4 lattice. Luminescence decays and spectral features at each site depend strongly on temperature and Eu 3+ -concentration in BaY 2 O 4 :Eu 3+ .

Eu2+-doped CsMgPO4 phosphors were synthesized by the conventional high-temperature solid-state reaction. The phase formations of the phosphors were confirmed by X-ray powder diffraction measurements. The photoluminescence excitation and emission spectra, the temperature dependent (10–300 K) luminescence intensities and the decay curves of the phosphor were measured. The Eu2+-doped CsMgPO4 shows a red emission band peaking at around 650 nm from 4f65d1→4f7 transitions of Eu2+ ions. The luminescence nature of CsMgPO4:Eu2+ is greatly different from the other Eu2+ doped ABPO4 orthophosphates (A and B are mono- and divalent cations, respectively) and is characterized by the red-shifted emission, the larger Stokes shift and a lower luminescence quenching temperature. The anomalous luminescence properties of CsMgPO4:Eu2+ are ascribed to impurity trapped exciton emission.

Red emission LaMoBO 6 :Eu 3+ phosphors were synthesized by solid-state reaction, and their photoluminescence properties were investigated for the first time. The results indicate that LaMoBO 6 :Eu 3+ phosphors have many advantages, such as lower synthesis temperature, strong absorption in the near-UV region, and excellent chromaticity coordinates. La 1-x MoBO 6 :xEu 3+ phosphors are promising candidates for phosphor-converted white light-emitting diodes.

The luminescent properties of Ce 3+ -activated Ca 2 BO 3 Cl with nominal composition Ca 2(1-x) Ce x Na x BO 3 Cl were investigated at room temperature and low temperature. There are two types of Ce 3+ -emitting centers in the phosphor due to different occupancies in the host Ca 2 BO 3 Cl. The influence of doping concentration on the preferential site occupancy was studied, and the resonant-type energy transfer from site 1 to site 2 was also confirmed. In addition, the optimal composition of phosphor was x = 0.06, which shows a bright blue emission and strong band absorption in the near-UV region.

The red-emitting phosphor Eu 3 BWO 9 was prepared by the Pechini method. The phosphor was characterized by X-ray powder diffraction, scanning electron microscope, and photoluminescence measurements. It can be efficiently excited by near-ultraviolet and blue light and exhibits the far stronger red luminescence than the commercial Y 2 O 2 S:Eu 3+ . The dependences of luminescence intensities and the color coordinates on the heating temperatures were investigated. The crystallographic site-occupations of Eu 3+ ions in Eu 3 BWO 9 were investigated by the site-selective excitation spectra in the 5 D 0 → 7 F 0 region. The strong red luminescence together with its thermal stability were discussed on the base of the Eu 3+ site distributions in Eu 3 BWO 9 host. The phosphor would be a promising red component for solid-state lighting devices based on InGaN or GaN light-emitting diodes.

SrZn 2 (PO 4 ) 2 doped with Eu 3+ ions was prepared by high temperature solid-state reaction. The site-selective excitation and emission spectroscopy and luminescence decay (lifetime) have been investigated in the 5 D 0 → 7 F 0 region by using a pulsed, tunable, and narrowband dye laser. We observed two crystallographic sites for Eu 3+ in SrZn 2 (PO 4 ) 2 below 250 K and energy transfer from Eu 3+ at one site to Eu 3+ at the other site. The Stark energy levels of Eu 3+ at two different sites were assigned from the site-selective emission spectra. The luminescence from Eu 3+ at one of the two sites was quenched at room temperature. The lifetime of Eu 3+ ions at the two sites is compared. The defect structures and charge compensation mechanisms are discussed.

Mn 2+ -doped NaCaPO 4 were synthesized by a solid-state reaction. The structure and luminescence were investigated. The main excitation bands located at a band extending from 380 to 450 nm could match the emission of UV light emitting diode chips. The phosphors exhibited the emission in the wavelength range of 600―750 nm. The luminescence showed a redshift with the increase in Mn 2+ doping concentrations. This color points could be tunable by controlling the doping of Mn 2+ in NaCaPO 4 . The thermal stability of the luminescence of Mn 2+ ions was evaluated at different temperatures. The doping mechanism of Mn 2+ ions was discussed.

A green-emitting phosphor, Eu 2+ -activated KCaPO 4 , was synthesized by a conventional solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurements. The photoluminescence excitation and emission spectra, the temperature-dependent luminescence intensities (293-438 K), and decay curves of the phosphor were measured. With increasing temperature, the emission bands show the abnormal blueshift with broadening bandwidth. The natures of the Eu 2+ emission in KCaPO 4 , e.g., the chromaticity coordinates, the luminescence quenching temperature, and the activation energy for thermal quenching (ΔE), were reported. The excitation spectra have been investigated in the 5 D 0 → 7 F 0 region for Eu 3+ ions in KCaPO 4 by using a pulsed, tunable, and narrow-band dye laser to detect the cation site of Ca 2+ in KCaP0 4 . The multiple sites structure of Eu 2+ ions in KMgPO 4 lattices were suggested and discussed.

The Sm 2+ -doped SrZn 2 (PO 4 ) 2 phosphor was prepared by the high temperature solid-state reaction method. The temperature-dependent emission spectra and luminescence decay of Sm 2+ ions were investigated from 10 to 300 K. The investigation was focused on the site distributions of Sm 2+ ions in this host, which exhibited different spectroscopic features at varying temperatures. Two crystallography sites existed for Sm 2+ ions in this host below 170 K, where no energy transfer could be detected between them. However, only one Sm 2+ site was left from 170 K to room temperature. The photostability of the Sm 2+ ion was evaluated by the photobleaching method. This investigation would be helpful for understanding the doping mechanism and applications of rare-earth ions doped in this phosphate host.

Ternary orthophosphate [Sr 3 Sm(PO 4 )3] with a stoichiometric component of Sm 3+ ion was prepared by a solid-state reaction. The phase formation of the sample was investigated by X-ray powder diffraction measurement. Samarium ions can be incorporated into two forms, divalent and trivalent. Exposure to X-ray irradiation can cause Sm 3+ → Sm 2+ conversion in this host. The samples were investigated by photoluminescence and lifetime measurements. After excitation into the 4f 5 5d 1 levels, the Sm 2+ ions showed 5 D 0 → 7 F j , (J = 0, 1, 2) emission together with the broad band of 5d → 4f transition. The luminescence of Sm 2+ ions was sensitive to the temperature. With increasing temperature, the luminescence intensity of 5d → 4f emission band of Sm 2+ ions appeared and got stronger. The stability of an Sm 2+ ions created by X-ray irradiation was investigated by photobleaching under excitation at 488 nm of Ar + laser. The defects created by X-ray irradiation were briefly discussed. These results would be helpful to understand the reduction mechanism of Sm 2+ ion in the Sm 3+ concentrated host. © 2009 The Electrochemical Society. [DOI: 10.1149/1.3153142] All rights reserved.

A red-emitting phosphor, Eu 3+ -doped Ca 9 ZnLi(PO 4 ) 7 , was synthesized by the solid reaction-sintering process. The morphological features of the phosphor were investigated by scanning electron microscopy. The photoluminescence excitation and emission spectra, fluorescence decay curves, and the dependence of luminescence intensity on temperature were investigated. The phosphor can be excited by near-UV wavelength radiation to realize an intense red luminescence (613 nm) corresponding to the electric dipole transition 5 D 0 - 7 F 2 of Eu 3+ ions. The crystallographic site occupations of the Eu 3+ ions were investigated by the site-selective excitation spectra and the fluorescence decay in the 5 D 0 → 7 F 0 region under a pulsed, tunable, narrow band dye laser. The potential application of this phosphor for light-emitting diodes was evaluated by the dependence of luminescence and the color coordinates on temperature.