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摘要
Single crystals of GdCa4O(BO3)(3) (GdCOB) pure and doped with Eu concentration of 1 and 4 a% were grown by the Czochralski and micropulling-down methods. The distribution of Eu ions in GdCOB crystals was uniform. The substitutions of Eu3+ in Gd, Ca(1) and Ca(2) cation sites and eventually formation Eu2+ have been investigated. The spectroscopic properties of crystals are compared with the properties of nanopowders obtained by sol-gel method. Radioluminescence spectra of undoped GdCOB crystal show the characteristic emission of Gd3+ at about 312 nm, whereas this emission dramatically decreases in Eu-doped crystals upon X-ray excitation, as well as in Eu-doped nanopowders excited in vacuum ultraviolet (VUV) region. The VUV excitation in the range 125-333 nm for Eu-doped samples leads to strong emission in red coming from the D-5(0) multiplet of Eu3+, only. In the photoluminescence decay kinetics of 312 nm emissions substantial shortening and departure for single exponential decay in Eu-doped samples is clearly observed. Higher Eu doping results in further acceleration of the decay. In undoped GdCOB crystal, the lifetime of the Gd3+ P-6(7/2) multiplet is 2.79 ms. The Eu3+ 5 Do decay kinetics monitored at 613 nm are rather constant. Numerical fitting of fully exponential curves, reveals lifetimes 2.7 ms for nanopowder and 2.5 ms for single crystal. The results suggest that this material may be used as a red phosphor in plasma display panels in nanopowder form because of strong excitation band of Eu3+ luminescence in the 160-200 nm regions. Contrary to nanopowder sample, such an excitation band, attributed to the Gd3+-O2- charge transfer was not observed in crystal obtained by the micropulling-down method.
- 出版日期2007-12
