Abstract:The photoluminescence spectra and luminescence excitation spectra of pure microcrystalline and nano-sized ZnWO 4 as well as the Zn Ni 1− WO 4 solid solutions were studied using vacuum ultraviolet (VUV) synchrotron radiation. The samples were also characterized by x-ray powder diffraction. We found that: (i) the shape of the photoluminescence band at 2.5 eV, being due to radiative electron transitions within the [WO 6 ] 6− anions, becomes modulated by the optical absorption of Ni 2+ ions in the Zn Ni 1− WO 4 solid solutions; and (ii) no significant change in the excitation spectra of Zn 0 9 Ni 0 1 WO 4 is observed compared to pure ZnWO 4 . At the same time, a shift of the excitonic bands to smaller energies and a set of peaks, attributed to the one-electron transitions from the top of the valence band to quasi-localized states, were observed in the excitation spectrum of nano-sized ZnWO 4 .PACS (2008)

No abstract

No abstract

Comparative analysis of the luminescent properties of nanocrystalline LaPO 4 :Ce,Tb and YVO 4 :Eu luminescent materials with macrocrystalline analogues, commercially produced by Philips, has been performed under excitation by pulsed vacuum ultraviolet (VUV) synchrotron radiation, ranging from 3.7-40 eV. Special attention was paid to VUV spectral range, which is not reachable with commonly used lamp and laser sources. Our results clearly show distinct difference in the excitation spectra for nano-and macrocrystalline samples, especially at energies, when the spatial separation of electron-hole pairs is comparable with sizes of nanoparticles. Differences in the region of multiplication of the electronic excitations are also demonstrated and discussed.

Photoluminescence and excitation spectra of microcrystalline and nanocrystalline nickel tungstate (NiWO 4 ) were measured using UV-VUV synchrotron radiation source. The origin of the bands is interpreted using comparative analysis with isostructural ZnWO 4 tungstate and based on the results of recent first-principles band structure calculations. The influence of the local atomic structure relaxation and of Ni 2+ intra-ion d-d transitions on the photoluminescence band intensity are discussed.