Cheng-Jun Duan

Vacuum ultraviolet spectroscopic properties of rare earth (RE=Ce,Tb,Eu,Tm,Sm)-doped hexagonal KCaGd(PO4)2 phosphate

Hexagonal KCaGd(PO4)2:RE3+ (RE=Ce,Tb,Eu,Tm,Sm) were synthesized by coprecipitation method and their vacuum ultraviolet–ultraviolet (VUV-UV) spectroscopic properties were investigated. The bands at about 165nm in the VUV excitation spectra are attributed to the host lattice absorptions. For Ce3+-doped samples, the bands at 207, 256, 275, and 320nm are assigned to the 4f-5d transitions of Ce3+ in KCaGd(PO4)2. For Tb3+-doped sample, the bands at 203 and 222nm are related to the 4f-5d spin-allowed transitions. For Eu3+-doped sample, the O2−–Eu3+ charge-transfer band (CTB) at 229nm is observed, and the fine emission spectrum of Eu3+ indicates that Eu3+ ions prefer to occupy Gd3+ or Ca2+ sites in the host lattice. For Tm3+- and Sm3+-doped samples, the O2−–Tm3+ and O2−–Sm3+ CTBs are observed to be at 176 and 186nm, respectively. From the standpoints of the absorption band, color purity, and luminescent intensity, Tb3+-doped KCaGd(PO4)2 is a potential candidate for 172nm excited green plasma display phosphors.

Luminescent properties of REBa3B9O18 (RE = Lu, Tb, Gd, Eu) under VUV excitation

The VUV excited luminescent properties of REBa3B9O18 (RE = Lu, Tb, Gd, Eu) were investigated. The bands near 160 nm in the VUV excitation spectra of those compounds are attributed to the host absorptions; at the same time, the energy of host absorption is shifted to a higher energy region with decreasing RE3+ radius. It is observed that there is energy transfer between the hosts and luminescent centres (e.g. Tb3+, Gd3+ and Eu3+). From the standpoints of colour purity and luminescent efficiency, the phosphor of TbBa3B9O18 is an attractive candidate for new green-emitting phosphors for plasma display panels and mercury-free fluorescent lamps.

Ba3BP3O12:Eu2+—A potential scintillation material

The sample of Eu2+-doped Ba3BP3O12 was prepared by a solid-state reaction at high temperature and was showed to be an excellent scintillator when excited with hard x ray s. The phosphor showed a broad emission band in the wavelength range of 400–650 nm and a comparable light yield with that of Bi4Ge3O12 powders. Its room temperature fluorescence decay curve exhibited a two-exponent shape with decay time of 20.0±1.4ns (98.97%) and 522±9ns (1.03%), respectively. Considering the suitable emission wavelength range, large light yield, short decay time, moderate density, moderately low melting point, and nonhygroscopic property of Ba3BP3O12:Eu2+, one has reason to assume that this compound might find an application as a new scintillation material.

Spectral properties and energy transfer in PbWO~4 co-doped with Cr^3^+ and F^-

A Cr(3+), F(-)-co-doped PbWO(4) crystal was grown by the Czochralski method and its spectroscopic properties were investigated. In addition to the intrinsic luminescence of PbWO(4), the sample showed [Formula: see text] radiation of Cr(3+) excited by x-radiation or UV-vis light. This indicated that the Cr(3+) is submitted to a strong crystal field and a doping mechanism is hereby proposed that Cr(3+) replaces W(6+) with the cooperation of F(-). The reabsorption and resonant energy transfer mechanisms from host to Cr(3+) were studied. As a result, the PbWO(4) intrinsic emission was intensively suppressed and the [Formula: see text] luminescence increased when excited by x-radiation compared to excitation by UV-vis light, and the decay constants of PbWO(4) host scintillation reduce. The significant [Formula: see text] luminescence of this material may be of interest for further application.