Nanosized Y2O3:Eu was synthesized by using a solution–combustion method. The samples were characterized by x-ray diffraction, extended x-ray absorption fine structure (EXAFS), and photoluminescence spectroscopy. Our EXAFS result showed that the local environments surrounding both Y and Eu atoms had obviously changed when the particle size was smaller than 10 nm. The coordination number and the bond length of Y (Eu)–O shell increased and the disorder became larger. This change also produced an emission peak and the charge-transfer band showed an unusual redshift as the particle size decreased. The luminescence properties can be explained by use of the EXAFS results.

The white-light long-lasting phosphor CaAl2O4:Dy3+ was prepared and investigated. The white-light afterglow spectra under the irradiation of 254 or 365nm are comprised of the blue light emission and the yellow light emission, originating from the transitions of F9∕24→H15∕26, F9∕24→H13∕26 in the 4f9 configuration of Dy3+. The afterglow can last 32min for the best sample with Dy-doped concentration of 2at.%. The decay curve and the thermoluminescence curve show to be a second-order process. Thermoluminescence curves exhibit a complicated structure in the range of 230–450K with the peaks at 244, 280, 310, and 346K. The two thermoluminescence bands peaking above room temperature have corresponding traps with the depths of 0.54 and 0.61eV, which are responsible for the afterglow emission at room temperature. This work provides a promising approach for the development of white-light long-lasting phosphor.

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In our recent study Xu et al (2002 Chem. Phys. Lett. 364 57-63), a phase transformation from the hexagonal to the tetragonal structure in the annealed ZnO films on silicon was studied by atomic force microscopy. Cathodoluminescence (CL) and glancing-angle x-ray diffraction analysis of the ZnO films indicated that such a transformation is due to the generation of a tetragonal zinc silicate. In order to identify the formation mechanism of the zinc silicate and the bottom broadening of the UV band, a depth profile secondary ion mass spectroscopy experiment was carried out. The results show that vast atomic diffusion between the ZnO film and the silicon substrate occurred due to the annealing temperature. Such interdiffusion can create not only a mixed crystal of ZnO and Zn 2 SiO 4 , but also an amorphous silicon dioxide (a-SiO 2) in a deep range from the surface to the interface of the ZnO/Si system. The a-SiO 2 is most probably the source of the 453 nm blue band hidden in the tail of the 390 nm UV band, since the blue band agrees with the CL spectra of the amorphous quartz glass and the thermally oxidized silicon. ZnO film has been widely studied for a variety of applications in piezoelectric acoustic wave devices [1, 2], varistors [3, 4], optical waveguides [5], substrates or buffer layers for the growth of GaN [6, 7], or as a material for light-emitting diodes [8]. In addition, ZnO deposited on silicate glass has been widely used as a transparent conducting oxide buffer in the construction of semiconductor film solar cells [9]. A ZnO/Si heterojunction was also investigated as a candidate for a mono-junction solar cell [10]. Under such conditions, it is necessary to

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The luminescence of two newly developed blue-emitting long afterglow phosphors, Sr 2Àx Ca x MgSi 2 O 7 :Eu 2+ , Dy 3+ (x ¼ 0, 1), has been studied. The emission under VUV-UV excitation from a synchrotron radiation source, along with the long afterglow spectra have been measured at different temperatures ranging from 7 to 300 K. While the emission spectra under 170 nm excitation exhibit both the 5d-4f transitions of Eu 2+ and 4f-4f transitions of Dy 3+ , only the blue band corresponding to the 5d-4f transitions of Eu 2+ is observed in the long afterglow spectra. Emission of Sr 2 MgSi 2 O 7 :Eu 2+ , Dy 3+ excited by an intense VUV laser source (157.6 nm) is also reported. The rich line structures in the laser-excited emission spectra partly result from 4f-4f transitions of Eu 3+ , indicating an efficient photon-induced process, which promotes Eu 2+ to Eu 3+ . The thermoluminescence covering the temperature range from 50 to 450 K for both samples has been measured as well and the depth of the traps responsible for the long afterglow emission was estimated. The mechanism of the persistent luminescence and the origin of the traps are discussed in the light of these results. r