Eu 2þ -activated LiBaPO 4 phosphor was synthesized by conventional solid-state reaction. The photoluminescence excitation and emission spectra, the temperature dependent luminescence intensities (12-450 K), and decay curves of the phosphor were investigated. With the increasing of temperatures, the emission bands of LiBaPO 4 :Eu 2þ show the abnormal blue-shift and the decreasing of emission intensity. The natures of the Eu 2þ emission in LiBaPO 4 , for example, the luminescence quenching temperature, and the activation energy for thermal quenching (ΔE), were reported. The afterglow fluorescence was detected in LiBaPO 4 :Eu 2þ phosphor. Together with the Eu 2þ luminescence, Eu 3þ ions with the abnormal crystal field were observed. The site-selective excitation in the 5 D 0 f 7 F 0 region for Eu 3þ ions, emission spectra, and decay curves have been investigated using a pulsed, tunable, and narrowband dye laser to detect the microstructure and crystallographic surrounding of Eu 3þ,2þ at Ba 2þ sites in LiBaPO 4 . The multiple sites structure of Eu 2þ and Eu 3þ ions in LiBaPO 4 lattices was suggested. The lower quenching temperature, afterglow, and luminescence mechanism were discussed. The photoluminescence quantum efficiencies of LiBaPO 4 :Eu 2þ were measured and compared with the reported phosphors. Different from the published data on LiBaPO 4 :Eu 2þ , this investigation indicates that LiBaPO 4 :Eu 2þ is not a good phosphor candidate applied in white light emitting diode.

Eu(2+)-doped monophosphates NaSrPO(4) and KBaPO(4) with the β-K(2)SO(4) structure were synthesized using the conventional high temperature solid state reaction. The X-ray powder diffraction, photoluminescence excitation, and emission spectra and decay curves were measured. The phosphors can be efficiently excited by UV-visible light from 220 to 430 nm to realize emission in the visible range. The natures of the Eu(2+) emission, e.g., the chromaticity coordinates, the Stokes shifts, and the luminescence absolute quantum efficiencies, were reported. The luminescence quenching temperatures and the thermal activation energies for NaSrPO(4):Eu(2+) and KBaPO(4):Eu(2+) were obtained from the temperature dependent (10-435 K) luminescence intensities and decay curves. KBaPO(4):Eu(2+) presents only one emission center; however, Eu(2+) ions have a "disordered environment" in NaSrPO(4) lattices. The relationship between the luminescence thermal stabilities and the crystal structures was discussed. The crystallographic occupations of rare earth ions doped in these hosts were analyzed by the site-selective emission spectra and the excitation spectra of Eu(3+) ions in the (7)F(0)→(5)D(0) transitions using a pulsed, tunable, and narrow-band dye laser. In KBaPO(4), the Eu(3+) ions could be distributed in the host with a high "ordered state" in only one site in the lattices. However, the multiple site structure of Eu(3+) ions with highly disordered distributions in NaSrPO(4) lattices was suggested.

An Eu(2+)-doped LiMgPO(4) phosphor was prepared by a high temperature solid-state reaction. The formation was confirmed by x-ray powder diffraction measurements to be a single LiMgPO(4) phase. The photoluminescence excitation and emission spectra were investigated. The luminescence shows a broad emission from the 4f(6)5d → 4f(7)(8)S7/2) transition at room temperature. At low temperature the zero-phonon line for transitions to the 4f(7) ((8)S(7/2)) level of the 4f(6)(7)Fj)5d1 excited state is observed at 360 nm and it is found that the emission line of the 4f(7)(6)P7/2) → 4f(7)(8)S7/2) transition overlaps the zero-phonon line at nearly the same position of 360 nm. The influences of temperature on the luminescence spectra and decay times were investigated. The doping mechanism of Eu(2+) ions in LiMgPO(4) was discussed. The Eu(2+) ions were suggested to occupy the Li(+) sites in LiMgPO(4) to induce the small crystal field splitting and weak nephelauxetic effect.

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 K͒, 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 ͑⌬E͒, 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 KCaPO 4 . The multiple sites structure of Eu 2+ ions in KMgPO 4 lattices were suggested and discussed.

The Eu 21 -doped NaBaPO 4 phosphor was prepared by hightemperature solid-state reaction. The photoluminescence excitation and emission spectra and the luminescence quantum efficiency of Eu 21 ions were investigated. The dependence of luminescence intensity on temperatures and the temperaturedependent decay times of Eu 21 ions doped in NaBaPO 4 were measured and discussed. The natures of the Eu 21 emission in NaBaPO 4 , e.g., the Stokes shift, the luminescence quenching temperature (T 0.5 ), the activation energy for thermal quenching (dE) were reported. In addition, the crystal structure and the site occupancy of Eu 21 ions doped in NaBaPO 4 crystal lattice were discussed. Two different Eu 21 centers were assigned according to the crystal structure and the luminescence characteristics of Eu 21 ions. The phosphor shows an excellent thermal stability on temperature quenching effects. With the increasing of temperature, the emission bands show the abnormal blue-shift.