Suyin Zhang

The luminescence characterization and structure of Eu2 + doped LiMgPO4

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.

The Spectroscopy and Structural Sites of Eu2 + Ions Doped KCaPO4 Phosphor

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.

Tunable Red Luminescence of Mn2 + -Doped NaCaPO4 Phosphors

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.

Luminescence Properties of Yb2+ Doped NaBaPO4 Phosphate Crystals

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.